JPH11121913A - Formation of printed board and solder bump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase mechanical strength of a junction face between a substrate and a solder bump by positioning a solder ball on a pad which is arranged protruding from a solder resist on the substrate and then melting the solder ball by heat treatment and thereby forming the solder bump which covers an upper face and an external surface of the pad. SOLUTION: A pad 4 is formed thicker than a solder resist 5a so that the surface of the pad 4 may be protruded from that of the solder resist 5a formed on a substrate 1a. Then, flux 7 is deposited onto the surface of the pad 4 and a solder ball 6 is positioned on the pad 4 through the flux 7. By this method, the solder ball 6 melts into such a shape as to wrap up the protruding pad 4 and thereby a hemispherical solder bump is formed on the pad 4. Therefore, a junction area between the substrate 1 and the solder bump increases and there are not voids in a junction face between the substrate 1 and the solder bump and thereby a junction strength between the substrate 1 and the solder bump can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed circuit board in which a solder pump obtained by melting a solder ball is applied to a pad provided on the board.

[0002]

2. Description of the Related Art BGA (ball grid array) and C
The SP (chip scale package) is responsible for downsizing, lightening, and multifunctional electronic components, and is a package having a connection method using ball bumps without using leads.
Conventionally, the structure of a substrate for BGA and CSP is such that pads (electrodes) 4 are formed on a substrate 1 as shown in FIG.
The solder resist 5 is printed at the same height as the pad 4 except for the pad 4. And IC
When manufacturing a motherboard for manufacturing a package device on which a package such as a package is mounted, a spherical solder ball 6 having a flux 7 adhered to the lower surface is mounted on the pad 4 and then the substrate 1 is heat-treated. Ball 6
To form a hemispherical solder bump on the pad 4.

FIG. 8 (a) shows, for example, Japanese Unexamined Patent Publication No.
FIG. 1 is a cross-sectional view of a substrate device for electric equipment described in Japanese Patent Application Laid-Open No. 64520, in which a through hole 2 is formed in a substrate 1.
Has a conductivity comprising a cylindrical portion 3p covering the inner surface of the through hole 2 and flange portions 3a and 3b provided at the upper and lower ends of the cylindrical portion 3p and covering the front and back surfaces of the substrate. A connector 3 is provided. The flange portions 3a and 3b are
Each functions as an electrode portion on the front surface and the back surface of the substrate 1.
On both surfaces of the substrate 1, solder resists 5a and 5b are applied except for the electrode portions such as the flange portions 3a and 3b. The thickness of the solder resist 5b on the back surface of the substrate is substantially equal to the thickness of the flange 3b.
The thickness of the solder resist 5a on the substrate surface is formed to be thicker than the thickness of the flange portion 3a, and a cylindrical concave portion 14 is formed on the upper portion of the flange portion 3a and is surrounded by the solder resist 5a. Is done. The solder balls 6 are temporarily held in the concave portions 14 and hemispherical solder bumps are formed on the solder bonding surface 15 on the upper surface of the flange portion 3a through heat treatment.

[0004]

Generally, when the holding position of the solder ball 6 is shifted, if the size of the shift is not more than 1/2 of the diameter of the solder ball 6, the self-alignment effect during the heat treatment is reduced. It is said that the solder ball 6 returns to a predetermined position, but in the conventional ball grid array package substrate as shown in FIG. 7, the surface of the pad 4 and the surface of the solder resist 5 are at the same height. Since it was formed, the solder bumps were only attached to the upper surfaces of the pads 4, so that a sufficiently large bonding strength could not be obtained.
In particular, when the solder ball 6A is mounted with a large deviation from a predetermined position, the solder ball hardly returns to the center of the pad 4 even when heat treatment is performed, and the solder bump is placed at a predetermined position on the substrate 1. Can not be formed,
As a result, there is a problem that it is difficult to obtain a sufficiently large bonding strength. Further, in the board apparatus for electric equipment described in Japanese Patent Application Laid-Open No. 9-64520, the solder balls 6 are temporarily held in the concave portions 14 provided at positions corresponding to the connectors 3, so that the solder balls 6 Does not significantly deviate from the position of. However, in the above example, a closed space is formed at the boundary between the solder ball 6 and the lower side surface of the concave portion 14 and the solder joint surface 15 in a state where the solder ball 6 is temporarily held. When the heat treatment is performed, FIG.
As shown in (b), a void V remains at the boundary between the lower side surface of the recess 14 and the solder joint surface 15. Further, in this case, since the hole of the cylindrical portion 3p of the connector 3 is a fine hole, it is difficult for molten solder to enter therein. Therefore, in this case, the solder does not adhere to the outer peripheral portion of the solder joint surface 15 which is the upper surface of the flange portion 3a of the connector 3, so that a sufficient joint strength cannot be obtained. When such a substrate is soldered to a package such as an IC as a motherboard, the reflow resistance is poor, and when a reliability test such as a heat cycle or a high-temperature and high-humidity environmental test is performed, the above void is generated. There has been a problem that the reliability of the package device is reduced, for example, a solder crack or separation of the motherboard from the package occurs due to the expansion phenomenon of V.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a printed circuit board which reliably holds a solder ball at a predetermined position and has improved mechanical strength at a joint surface with the board. It is an object of the present invention to provide a method of manufacturing a package device using the same.

[0006]

According to a first aspect of the present invention, there is provided a printed circuit board wherein a surface of a pad is projected from a surface of a solder resist formed on the substrate.

Further, the printed circuit board according to claim 2 is:
A concave portion is provided in the center of the pad, or the shape of the pad is annular.

According to a third aspect of the present invention, the thickness of the periphery of the pad of the solder resist formed on the substrate is larger than the thickness of the pad.

According to a fourth aspect of the present invention, there is provided the printed circuit board manufacturing method according to any one of the first to third aspects, wherein the solder ball is melted after positioning the solder ball at a position corresponding to the pad. The solder bumps are formed on the surface of the pad and its periphery.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1 FIG. FIG. 1 is a cross-sectional view of a main part in a state where solder balls are mounted on a substrate for a ball grid array package device according to Embodiment 1 of the present invention. A through hole 2 is formed in the substrate 1 for a ball grid array package. At the same time, a recess 1p for an electrode pattern is formed on the side of the through-hole 2 on the substrate surface 1a. The substrate 1 has a cylindrical portion 3p covering the inner surface of the through hole 2 and an oblong upper pattern 3 provided at the upper end of the cylindrical portion 3p and covering the concave portion 1p of the substrate 1.
A connector 3 having conductivity, which is provided at the lower end of the cylindrical portion 3p and has an oblong lower pattern 3r that covers the back surface 1b of the substrate 1, is provided. A disc-shaped pad (electrode) 4 is formed on the upper pattern 3q so as to avoid the through hole 2. Solder resists 5a and 5b are applied to both surfaces of the substrate 1, except for the electrodes such as the pads 4 and the lower pattern 3r. Although the thickness of the lower pattern 3r is substantially equal to the thickness of the solder resist 5b formed on the back surface 1b of the substrate, the thickness of the pad 4 is larger than that of the solder resist 5a formed on the front surface 1a of the substrate. It is formed thicker than the solder resist 5a so that the surface protrudes. A flux 7 is attached to the surface of the pad 4, and a solder ball 6 is positioned and mounted thereon. The flux 7 is used to hold the solder ball 6 on the pad 4 and to improve the wettability between the solder ball 6 and the pad 4 when the solder ball 6 is melted during heat treatment. A material of about 300 Pa · s is used. In the above-described state, when the ball grid array substrate 1 is put into, for example, a heating furnace and heat treatment is performed, the solder balls 6 are melted and cover not only the upper surface of the protruding pad 4 but also the outer periphery 4a thereof. Thus, the pad 4 is melted so as to wrap the entire pad 4, and a hemispherical ball grid (solder bump) is formed on the pad 4. Further, since the molten solder is in contact with the pad 4 so as to surround the pad 4, no void is generated on the solder joint surface. As described above, since the solder bumps are formed on the upper surface and the outer periphery of the pad 4, the bonding strength of the solder bumps can be increased.

As described above, in the first embodiment,
Since the thickness of the pad 4 is made to protrude from the surface of the solder resist 5 a formed on the substrate 1, the solder ball 6 is melted so as to wrap the whole of the protruding pad 4, and Has hemispherical solder bumps. Therefore, not only does the bonding area between the substrate 1 and the solder bumps increase, but also no void is generated on the solder bonding surface, so that the bonding strength between the substrate 1 and the formed solder bumps is improved.

In the first embodiment, the substrate 1
Used a double-sided board having a joint 3
In the case of a pad 4 on which the connector 3 is not provided or a single-sided substrate 8 as shown in FIG. 2, the surface of the pad 4 is made to protrude more than the surface of the solder resist 5 formed on the surface of the substrate 8. If solder balls 6 are mounted on the pads 4 and heat treatment is performed, the bonding strength between the substrate 8 and the formed solder bumps can be improved. Further, the substrate 1 or the substrate 8 is not limited to a substrate for a ball grid array package device,
It goes without saying that a printed circuit board for high-density mounting using solder balls, such as a chip scale package board, may be used.

Embodiment 2 FIG. FIG. 3 is a cross-sectional view of a principal part in a state in which solder balls are mounted on a substrate for a ball grid array package device according to a second embodiment of the present invention. The shape is formed in a ring shape, and the solder resist in the ring is removed. Further, the thickness of the pad 4 and the thickness of the solder resist 5a were formed substantially the same. A solder ball 6 having a flux 7 adhered to the lower surface is positioned and mounted at the center of the surface of the pad 4. Flux 7 above
Are the same as those used in the first embodiment. When the heat treatment of the ball grid array package substrate 1 is performed in this state, the solder balls 6 melt around the center of the pads 4 to form hemispherical solder bumps. At this time, even when the center position of the solder ball 6 is displaced from the center portion of the pad 4, the viscosity of the flux 7 decreases before the melting of the solder ball during the heat treatment. It moves to the center of the surface of the pad 4. Therefore, the solder ball 6 is melted and solidified at the center of the surface of the pad 4 in a state where the contact area between the solder ball 6 and the pad 4 is large. Further, since the molten solder is in contact with only the pad 4, no void is generated on the solder joint surface. Although the pad 4 has been described as being ring-shaped with a through hole in the center, a pad having a recess on the center may be formed by performing the electrode forming step twice or the like. In this case, since the pad 4 and the solder ball 6 are in contact even on the bottom surface, the contact area with the pad 4 can be further increased.

As described above, in the second embodiment,
Since the shape of the pad 4 is ring-shaped, the solder ball 6 moves to the center of the surface of the pad 4 and melts during the heat treatment even if the solder ball 6 is mounted at a position shifted from a predetermined position. Therefore, solder bumps can be formed at predetermined positions on the substrate 1. Further, since the solder ball 6 and the pad 4 are in contact with each other at the outer peripheral portion of the solder ball 6, compared with the case where the solder ball 6 is mounted on a pad on a flat plate,
Since it is melted and solidified in a state where the contact area is large, the bonding strength between the substrate 1 and the formed solder bump is improved. Moreover, since the flux 7 is attached not only to the upper surface of the pad 4 but also to the inner peripheral surface of the ring, when the solder ball 6 is melted to form a solder bump, the flux 7 adheres to the inner peripheral surface of the pad 4. Therefore, the solder bumps are less likely to generate voids since they are wrapped around the whole.

In the second embodiment, the solder resist inside the ring is described as being removed. However, even if the solder resist 5r is formed inside the ring,
As shown in FIG. 4, if the thickness of the ring-shaped pad 4 is made larger than the thickness of the solder resist 5a, the pad 4
Since the solder bump can be integrated with the inner peripheral surface of the recess, the solder ball 6 can be melted and solidified with a larger contact area between the solder ball 6 and the pad 4. In addition, the mechanical strength at the joint surface can be further improved. Even if the solder resist 5r inside the ring is removed, the same high cost can be obtained. In addition, if the thickness of the pad 4 is formed larger than the thickness of the solder resist 5a and a pad provided with a depression on the center side is formed, the formed solder bump is also bonded to the bottom surface of the pad 4; Surface mechanical strength can be further improved.

Embodiment 3 FIG. 5 is a cross-sectional view of a principal part in a state in which solder balls are mounted on a substrate for a ball grid array package device according to Embodiment 3 of the present invention. The thickness of the solder resist 5a formed on the substrate surface 1a is increased.
The surface of the solder resist 5 a around the pad 4 is formed higher than the surface of the pad 4. A part of the solder resist 5a corresponding to the surface of the pad 4 is removed to have an inverted trapezoidal cross section, thereby forming a mortar-shaped recess 5R. A solder ball 6 having a flux 7 adhered to the lower surface is positioned and mounted at the center of the recess 5R. The flux 7 used is the same as that used in the first embodiment. When the heat treatment of the ball grid array package substrate 1 is performed in this state, the solder balls 6 melt around the center of the recess 5R, so that hemispherical solder bumps are formed over the entire surface of the pad 4. Is done. Further, since the concave portion 5R has a cross-sectional shape removed in an inverted trapezoidal shape, a closed space is not formed when the solder ball 6 is mounted in the concave portion, so that voids are generated between the pad 4 and the lower side surface of the concave portion 5R. In addition, since the solder bumps are formed on the entire surface of the pad 4, the bonding strength between the solder bump and the pad 4 is improved.

As described above, in the third embodiment,
The thickness of the solder resist 5a formed on the substrate at the peripheral portion of the pad 4 is made larger than the thickness of the pad 4 to form the mortar-shaped recess 5R, so that the solder ball 6 is held at a predetermined position. As a result, a solder bump can be formed at the center of the pad 4 and the bonding strength is improved. Further, since the recess 5R has an inverted trapezoidal cross section, no closed space is formed between the solder ball 6 and the recess 5R. In addition, generation of voids can be suppressed. Further, since the solder bump is formed on the entire surface of the pad 4, the bonding strength between the solder bump and the pad 4 can be improved.

In the third embodiment, the pads 4 are formed in a flat plate shape. However, the pads 4 are formed in a ring shape in the same manner as in the second embodiment so that the positional accuracy of the formation of the solder bumps and the formation of the solder bumps on the substrate 1 can be improved. The bonding strength of the solder bumps thus obtained can be further improved.

Embodiment 4 FIG. 6 is a schematic process diagram showing a method for manufacturing a ball grid array package device according to Embodiment 4 of the present invention. First, as shown in FIG. 6A, solder balls 6 are placed on a single-sided substrate 8 for a ball grid array package device on which ring-shaped pads 4 are arranged.
Is positioned and mounted. Next, the single-sided substrate 8 is subjected to a heat treatment to form a hemispherical solder bump 6S on the pad and mount a package such as an IC as shown in FIG. The motherboard 9 is manufactured. After that, as shown in FIG. 6C, the motherboard 9 is aligned with a separately manufactured ball grid array package 10 corresponding to the motherboard 9. The electrodes 11 of the ball grid array package 10 are preliminarily provided with a preliminary solder 12. Also,
In the figure, reference numeral 13 denotes a solder resist formed on the electrode side of the ball grid array package 10. Next, with the ball grid array package 10 mounted on the motherboard 9, the ball grid array package 10 is heated in a reflow oven to solder the ball grid array package 10 to the motherboard 9, as shown in FIG. An array package device is manufactured.

As described above, in the fourth embodiment,
The ball grid array package device was manufactured using the single-sided substrate 8 for the ball grid array package device on which the ring-shaped pads 4 were arranged.
In addition to the high positional accuracy of the solder bumps 6S formed on the substrate, the bonding strength between the solder bumps 6S and the motherboard 9 is high, and no voids are generated. Does not occur. Therefore, a highly reliable ball grid array package device can be manufactured.

In the fourth embodiment, the mother board 9 of the ball grid array package device is manufactured using the single-sided substrate 8 for the ball grid array package device on which the ring-shaped pads 4 are arranged. It is not limited. For example, FIG.
To the motherboard 9 of the ball grid array package device using the substrate 1 or the substrate 8 described in any one of FIGS.
May be produced. Further, the substrate is used as a substrate for a chip scale package, and in the same manner as in the fourth embodiment,
A chip scale package device can also be manufactured.

[0022]

As described above, in the printed circuit board according to the first aspect, the surface of the pad is made to protrude from the surface of the solder resist formed on the substrate. Since the solder bumps are formed by melting in such a way as to envelop the whole, not only the bonding area between the formed solder bumps and the pads becomes large, but also no voids are generated on the solder bonding surface, so that the substrate Bonding strength between the solder bumps and the solder bumps is improved.

In the printed circuit board according to the second aspect of the present invention, a concave portion is provided at the center of the pad or the pad is formed in an annular shape. In addition to increasing the bonding strength, the solder ball moves to the center of the pad surface in the melting process during heat treatment even if the solder ball is misaligned from the predetermined position on the pad. So
Solder bumps can be formed at predetermined positions on the substrate.

According to the third aspect of the present invention, since the thickness of the peripheral portion of the pad of the solder resist formed on the substrate is larger than the thickness of the pad, the solder ball is melted while being held at a predetermined position. Therefore, the solder bump is formed at the center of the pad, and the bonding strength between the solder bump and the substrate is improved.

According to a fourth aspect of the present invention, there is provided the printed circuit board manufacturing method according to any one of the first to third aspects, wherein the solder balls are positioned at positions corresponding to the pads, and then the solder balls are melted. Since the solder bumps are formed on the surface of the pad and the periphery thereof, the positional accuracy of the solder bumps is improved, and a highly reliable printed circuit board having high bonding strength can be manufactured.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a substrate for a ball grid array package device according to a first embodiment of the present invention.

FIG. 2 is another example of the substrate for a ball grid array package device according to the first embodiment of the present invention.

FIG. 3 is a sectional view of a main part of a substrate for a ball grid array package device according to a second embodiment of the present invention.

FIG. 4 is another example of the substrate for a ball grid array package device according to the second embodiment of the present invention.

FIG. 5 is a sectional view of a main part of a substrate for a ball grid array package device according to a third embodiment of the present invention.

FIG. 6 is a diagram illustrating a method of manufacturing a ball grid array package device according to a fourth embodiment of the present invention.

FIG. 7 is a sectional view of a main part of a conventional substrate for a ball grid array package device.

FIG. 8 is another example of a conventional substrate for a ball grid array package device.

[Explanation of symbols]

1 board for ball grid array package, 2 through holes, 3 connectors, 4 pads, 5, 5a, 5b solder resist, 6 solder balls, 7 flux, 8 single-sided board, 9 motherboard, 10 ball grid array package.

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[Procedure amendment]

[Submission date] October 21, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction contents]

[Document Name] Statement

[Title of the Invention] Method of forming printed circuit board and solder bump
Law

[Claims]

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed circuit board in which a solder pump obtained by melting a solder ball is applied to a pad provided on the board.

[0002]

2. Description of the Related Art BGA (ball grid array) and C
The SP (chip scale package) is responsible for downsizing, lightening, and multifunctional electronic components, and is a package having a connection method using ball bumps without using leads.
Conventionally, the structure of a substrate for BGA and CSP is such that pads (electrodes) 4 are formed on a substrate 1 as shown in FIG.
The solder resist 5 is printed at the same height as the pad 4 except for the pad 4. And IC
When manufacturing a motherboard for manufacturing a package device on which a package such as a package is mounted, a spherical solder ball 6 having a flux 7 adhered to the lower surface is mounted on the pad 4 and then the substrate 1 is heat-treated. Ball 6
To form a hemispherical solder bump on the pad 4.

FIG. 8 (a) shows, for example, Japanese Unexamined Patent Publication No.
FIG. 1 is a cross-sectional view of a substrate device for electric equipment described in Japanese Patent Application Laid-Open No. 64520, in which a through hole 2 is formed in a substrate 1.
Has a conductivity comprising a cylindrical portion 3p covering the inner surface of the through hole 2 and flange portions 3a and 3b provided at the upper and lower ends of the cylindrical portion 3p and covering the front and back surfaces of the substrate. A connector 3 is provided. The flange portions 3a and 3b are
Each functions as an electrode portion on the front surface and the back surface of the substrate 1.
On both surfaces of the substrate 1, solder resists 5a and 5b are applied except for the electrode portions such as the flange portions 3a and 3b. The thickness of the solder resist 5b on the back surface of the substrate is substantially equal to the thickness of the flange 3b.
The thickness of the solder resist 5a on the substrate surface is formed to be thicker than the thickness of the flange portion 3a, and a cylindrical concave portion 14 is formed on the upper portion of the flange portion 3a and is surrounded by the solder resist 5a. Is done. The solder balls 6 are temporarily held in the concave portions 14 and hemispherical solder bumps are formed on the solder bonding surface 15 on the upper surface of the flange portion 3a through heat treatment.

[0004]

Generally, when the holding position of the solder ball 6 is shifted, if the size of the shift is not more than 1/2 of the diameter of the solder ball 6, the self-alignment effect during the heat treatment is reduced. It is said that the solder ball 6 returns to a predetermined position, but in the conventional ball grid array package substrate as shown in FIG. 7, the surface of the pad 4 and the surface of the solder resist 5 are at the same height. Since it was formed, the solder bumps were only attached to the upper surfaces of the pads 4, so that a sufficiently large bonding strength could not be obtained.
In particular, when the solder ball 6A is mounted with a large deviation from a predetermined position, the solder ball hardly returns to the center of the pad 4 even when heat treatment is performed, and the solder bump is placed at a predetermined position on the substrate 1. Can not be formed,
As a result, there is a problem that it is difficult to obtain a sufficiently large bonding strength. Further, in the board apparatus for electric equipment described in Japanese Patent Application Laid-Open No. 9-64520, the solder balls 6 are temporarily held in the concave portions 14 provided at positions corresponding to the connectors 3, so that the solder balls 6 Does not significantly deviate from the position of. However, in the above example, a closed space is formed at the boundary between the solder ball 6 and the lower side surface of the concave portion 14 and the solder joint surface 15 in a state where the solder ball 6 is temporarily held. When the heat treatment is performed, FIG.
As shown in (b), a void V remains at the boundary between the lower side surface of the recess 14 and the solder joint surface 15. Further, in this case, since the hole of the cylindrical portion 3p of the connector 3 is a fine hole, it is difficult for molten solder to enter therein. Therefore, in this case, the solder does not adhere to the outer peripheral portion of the solder joint surface 15 which is the upper surface of the flange portion 3a of the connector 3, so that a sufficient joint strength cannot be obtained. When such a substrate is soldered to a package such as an IC as a motherboard, the reflow resistance is poor, and when a reliability test such as a heat cycle or a high-temperature and high-humidity environmental test is performed, the above void is generated. There has been a problem that the reliability of the package device is reduced, for example, a solder crack or separation of the motherboard from the package occurs due to the expansion phenomenon of V.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a printed circuit board which reliably holds a solder ball at a predetermined position and has improved mechanical strength at a joint surface with the board. It is an object of the present invention to provide a method of manufacturing a package device using the same.

[0006]

Means for Solving the Problems According to claim 1 of the present invention.
Solder bumps are formed on the board using solder resist.
Position solder balls on protruding pads
After that, the solder ball is melted by heat treatment,
Form solder bumps attached to the pad upper surface and outer peripheral surface
That's what I did.

[0007] A solder van according to claim 2 of the present invention.
The method for forming the pad is based on the inner circumference of the annular pad disposed on the substrate.
After positioning the solder ball on the
The ball is melted and adhered to the upper and inner peripheral surfaces of the pad.
In this case, the solder bumps are formed.

[0008] A print according to claim 3 of the present invention.
The board has solder balls on the upper surface of the pads arranged on the board.
Position and melt the solder ball by heat treatment.
Printed circuit board with solder bumps formed on the upper surface of the pad
And a depression is formed on the upper surface of the pad.
Things.

Further , a print according to claim 4 of the present invention.
The board has solder balls on the upper surface of the pads arranged on the board.
Position and melt the solder ball by heat treatment.
Printed circuit board with solder bumps formed on the upper surface of the pad
Of the solder resist formed around the pad.
As the thickness moves away from the outer periphery of the pad,
It is configured to be formed so that it becomes gradually larger than the thickness.
It is a thing.

Further, the pudding according to claim 5 of the present invention.
The printed circuit board is the printed circuit board according to claim 4, wherein
A mortar-shaped recess in the solder resist around the pad
It is configured as follows.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1 FIG. FIG. 1 is a cross-sectional view of a main part in a state where solder balls are mounted on a substrate for a ball grid array package device according to Embodiment 1 of the present invention. A through hole 2 is formed in the substrate 1 for a ball grid array package. At the same time, a recess 1p for an electrode pattern is formed on the side of the through-hole 2 on the substrate surface 1a. The substrate 1 has a cylindrical portion 3p covering the inner surface of the through hole 2 and an oblong upper pattern 3 provided at the upper end of the cylindrical portion 3p and covering the concave portion 1p of the substrate 1.
A connector 3 having conductivity, which is provided at the lower end of the cylindrical portion 3p and has an oblong lower pattern 3r that covers the back surface 1b of the substrate 1, is provided. A disc-shaped pad (electrode) 4 is formed on the upper pattern 3q so as to avoid the through hole 2. Solder resists 5a and 5b are applied to both surfaces of the substrate 1, except for the electrodes such as the pads 4 and the lower pattern 3r. Although the thickness of the lower pattern 3r is substantially equal to the thickness of the solder resist 5b formed on the back surface 1b of the substrate, the thickness of the pad 4 is larger than that of the solder resist 5a formed on the front surface 1a of the substrate. It is formed thicker than the solder resist 5a so that the surface protrudes. A flux 7 is attached to the surface of the pad 4, and a solder ball 6 is positioned and mounted thereon. The flux 7 is used to hold the solder ball 6 on the pad 4 and to improve the wettability between the solder ball 6 and the pad 4 when the solder ball 6 is melted during heat treatment. A material of about 300 Pa · s is used. In the above-described state, when the ball grid array substrate 1 is put into, for example, a heating furnace and heat treatment is performed, the solder balls 6 are melted and cover not only the upper surface of the protruding pad 4 but also the outer periphery 4a thereof. Thus, the pad 4 is melted so as to wrap the entire pad 4, and a hemispherical ball grid (solder bump) is formed on the pad 4. Further, since the molten solder is in contact with the pad 4 so as to surround the pad 4, no void is generated on the solder joint surface. As described above, since the solder bumps are formed on the upper surface and the outer periphery of the pad 4, the bonding strength of the solder bumps can be increased.

As described above, in the first embodiment,
Since the thickness of the pad 4 is made to protrude from the surface of the solder resist 5 a formed on the substrate 1, the solder ball 6 is melted so as to wrap the whole of the protruding pad 4, and Has hemispherical solder bumps. Therefore, not only does the bonding area between the substrate 1 and the solder bumps increase, but also no void is generated on the solder bonding surface, so that the bonding strength between the substrate 1 and the formed solder bumps is improved.

In the first embodiment, the substrate 1
Used a double-sided board having a joint 3
In the case of a pad 4 on which the connector 3 is not provided or a single-sided substrate 8 as shown in FIG. 2, the surface of the pad 4 is made to protrude more than the surface of the solder resist 5 formed on the surface of the substrate 8. If solder balls 6 are mounted on the pads 4 and heat treatment is performed, the bonding strength between the substrate 8 and the formed solder bumps can be improved. Further, the substrate 1 or the substrate 8 is not limited to a substrate for a ball grid array package device,
It goes without saying that a printed circuit board for high-density mounting using solder balls, such as a chip scale package board, may be used.

Embodiment 2 FIG. FIG. 3 is a cross-sectional view of a principal part in a state in which solder balls are mounted on a substrate for a ball grid array package device according to a second embodiment of the present invention. The shape is formed in a ring shape, and the solder resist in the ring is removed. Further, the thickness of the pad 4 and the thickness of the solder resist 5a were formed substantially the same. A solder ball 6 having a flux 7 adhered to the lower surface is positioned and mounted at the center of the surface of the pad 4. Flux 7 above
Are the same as those used in the first embodiment. When the heat treatment of the ball grid array package substrate 1 is performed in this state, the solder balls 6 melt around the center of the pads 4 to form hemispherical solder bumps. At this time, even when the center position of the solder ball 6 is displaced from the center portion of the pad 4, the viscosity of the flux 7 decreases before the melting of the solder ball during the heat treatment. It moves to the center of the surface of the pad 4. Therefore, the solder ball 6 is melted and solidified at the center of the surface of the pad 4 in a state where the contact area between the solder ball 6 and the pad 4 is large. Further, since the molten solder is in contact with only the pad 4, no void is generated on the solder joint surface. Although the pad 4 has been described as being ring-shaped with a through hole in the center, a pad having a recess on the center may be formed by performing the electrode forming step twice or the like. In this case, since the pad 4 and the solder ball 6 are in contact even on the bottom surface, the contact area with the pad 4 can be further increased.

As described above, in the second embodiment,
Since the shape of the pad 4 is ring-shaped, the solder ball 6 moves to the center of the surface of the pad 4 and melts during the heat treatment even if the solder ball 6 is mounted at a position shifted from a predetermined position. Therefore, solder bumps can be formed at predetermined positions on the substrate 1. Further, since the solder ball 6 and the pad 4 are in contact with each other at the outer peripheral portion of the solder ball 6, compared with the case where the solder ball 6 is mounted on a pad on a flat plate,
Since it is melted and solidified in a state where the contact area is large, the bonding strength between the substrate 1 and the formed solder bump is improved. Moreover, since the flux 7 is attached not only to the upper surface of the pad 4 but also to the inner peripheral surface of the ring, when the solder ball 6 is melted to form a solder bump, the flux 7 adheres to the inner peripheral surface of the pad 4. Therefore, the solder bumps are less likely to generate voids since they are wrapped around the whole.

In the second embodiment, the solder resist inside the ring is described as being removed. However, even if the solder resist 5r is formed inside the ring,
As shown in FIG. 4, if the thickness of the ring-shaped pad 4 is made larger than the thickness of the solder resist 5a, the pad 4
Since the solder bump can be integrated with the inner peripheral surface of the recess, the solder ball 6 can be melted and solidified with a larger contact area between the solder ball 6 and the pad 4. In addition, the mechanical strength at the joint surface can be further improved. Even if the solder resist 5r inside the ring is removed, the same high cost can be obtained. In addition, if the thickness of the pad 4 is formed larger than the thickness of the solder resist 5a and a pad provided with a depression on the center side is formed, the formed solder bump is also bonded to the bottom surface of the pad 4; Surface mechanical strength can be further improved.

Embodiment 3 FIG. 5 is a cross-sectional view of a principal part in a state in which solder balls are mounted on a substrate for a ball grid array package device according to Embodiment 3 of the present invention. The thickness of the solder resist 5a formed on the substrate surface 1a is increased.
The surface of the solder resist 5 a around the pad 4 is formed higher than the surface of the pad 4. A part of the solder resist 5a corresponding to the surface of the pad 4 is removed to have an inverted trapezoidal cross section, thereby forming a mortar-shaped recess 5R. A solder ball 6 having a flux 7 adhered to the lower surface is positioned and mounted at the center of the recess 5R. The flux 7 used is the same as that used in the first embodiment. When the heat treatment of the ball grid array package substrate 1 is performed in this state, the solder balls 6 melt around the center of the recess 5R, so that hemispherical solder bumps are formed over the entire surface of the pad 4. Is done. Further, since the concave portion 5R has a cross-sectional shape removed in an inverted trapezoidal shape, a closed space is not formed when the solder ball 6 is mounted in the concave portion, so that voids are generated between the pad 4 and the lower side surface of the concave portion 5R. In addition, since the solder bumps are formed on the entire surface of the pad 4, the bonding strength between the solder bump and the pad 4 is improved.

As described above, in the third embodiment,
The thickness of the solder resist 5a formed on the substrate at the peripheral portion of the pad 4 is made larger than the thickness of the pad 4 to form the mortar-shaped recess 5R, so that the solder ball 6 is held at a predetermined position. As a result, a solder bump can be formed at the center of the pad 4 and the bonding strength is improved. Further, since the recess 5R has an inverted trapezoidal cross section, no closed space is formed between the solder ball 6 and the recess 5R. In addition, generation of voids can be suppressed. Further, since the solder bump is formed on the entire surface of the pad 4, the bonding strength between the solder bump and the pad 4 can be improved.

In the third embodiment, the pad 4 is formed in a flat plate shape. However, by forming the pad 4 in a ring shape as in the second embodiment, the positional accuracy of the solder bump formation and the formation of the solder bump with the substrate 1 are improved. The bonding strength of the solder bumps thus obtained can be further improved.

Embodiment 4 FIG. 6 is a schematic process diagram showing a method for manufacturing a ball grid array package device according to Embodiment 4 of the present invention. First, as shown in FIG. 6A, solder balls 6 are placed on a single-sided substrate 8 for a ball grid array package device on which ring-shaped pads 4 are arranged.
Is positioned and mounted. Next, the single-sided substrate 8 is subjected to a heat treatment to form a hemispherical solder bump 6S on the pad and mount a package such as an IC as shown in FIG. The motherboard 9 is manufactured. After that, as shown in FIG. 6C, the motherboard 9 is aligned with a separately manufactured ball grid array package 10 corresponding to the motherboard 9. The electrodes 11 of the ball grid array package 10 are preliminarily provided with a preliminary solder 12. Also,
In the figure, reference numeral 13 denotes a solder resist formed on the electrode side of the ball grid array package 10. Next, with the ball grid array package 10 mounted on the motherboard 9, the ball grid array package 10 is heated in a reflow oven to solder the ball grid array package 10 to the motherboard 9, as shown in FIG. An array package device is manufactured.

As described above, in the fourth embodiment,
The ball grid array package device was manufactured using the single-sided substrate 8 for the ball grid array package device on which the ring-shaped pads 4 were arranged.
In addition to the high positional accuracy of the solder bumps 6S formed on the substrate, the bonding strength between the solder bumps 6S and the motherboard 9 is high, and no voids are generated. Does not occur. Therefore, a highly reliable ball grid array package device can be manufactured.

In the fourth embodiment, the motherboard 9 of the ball grid array package is manufactured using the single-sided substrate 8 for the ball grid array package in which the ring-shaped pads 4 are arranged. It is not limited. For example, FIG.
To the motherboard 9 of the ball grid array package device using the substrate 1 or the substrate 8 described in any one of FIGS.
May be produced. Further, the substrate is used as a substrate for a chip scale package, and in the same manner as in the fourth embodiment,
A chip scale package device can also be manufactured.

[0023]

As described above, the first aspect of the present invention is as follows.
The solder bump forming method according to
Position the solder balls on the pads that protrude from the
After deciding, melt the solder ball by heat treatment,
The solder bumps attached to the upper and outer peripheral surfaces of the pad
Solder bumps and pads
Not only increases the joint area with the solder joint, but also
Since no voids are generated, there is no
The joining strength is improved.

Further , a solder bun according to claim 2 of the present invention.
The method for forming the pad is based on the inner circumference of the annular pad disposed on the substrate.
After positioning the solder ball on the
The ball is melted and adhered to the upper and inner peripheral surfaces of the pad.
Solder bumps are formed.
Not only does the bonding area between the solder bump and the pad increase.
The solder ball is shifted from the above specified position.
Even if it is accidentally melted during the heat treatment,
Since it moves to a predetermined position on the circle,
Can be formed.

A print according to claim 3 of the present invention.
The substrate has a depression on the upper surface of the pad where the solder bumps are formed.
The bonding area between the solder bump and the pad is large
Not only does the solder ball
Even if it is set, it will melt when heat treated.
Melts and moves to a predetermined position on the upper surface of the pad.
A solder bump can be formed on the device.

A print according to claim 4 of the present invention.
The substrate is solder resist formed around the pads on the substrate.
As the thickness of the strike increases from the outer periphery of the pad,
Since it was formed so as to gradually increase the thickness of the pad,
While holding the solder ball in place on the pad,
The solder bumps are located at the center of the pad.
Formed, and the bonding strength is improved.

A print according to claim 5 of the present invention.
The substrate is mortar-shaped in the solder resist around the pad.
So that the solder ball is
It can be melted while holding it in place.
The bump is formed at the center of the pad, and the bonding strength is reduced.
improves.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a substrate for a ball grid array package device according to a first embodiment of the present invention.

FIG. 2 is another example of the substrate for a ball grid array package device according to the first embodiment of the present invention.

FIG. 3 is a sectional view of a main part of a substrate for a ball grid array package device according to a second embodiment of the present invention.

FIG. 4 is another example of the substrate for a ball grid array package device according to the second embodiment of the present invention.

FIG. 5 is a sectional view of a main part of a substrate for a ball grid array package device according to a third embodiment of the present invention.

FIG. 6 is a diagram illustrating a method of manufacturing a ball grid array package device according to a fourth embodiment of the present invention.

FIG. 7 is a sectional view of a main part of a conventional substrate for a ball grid array package device.

FIG. 8 is another example of a conventional substrate for a ball grid array package device.

[Description of Signs] 1 substrate for ball grid array package, 2 through hole, 3 connector, 4 pad, 5, 5a, 5b solder resist, 6 solder ball, 7 flux 8 single-sided substrate, 9 motherboard, 10 ball grid array package .

Claims (4)

[Claims] 1. A printed circuit board in which solder bumps are formed on pads provided on a board, wherein the surface of the pad is made to protrude from the surface of a solder resist formed on the board, and the protruding portion is formed. A printed circuit board, wherein substantially the entire surface of the printed circuit board is covered with the solder bump. 2. A printed circuit board in which a solder bump is formed on a pad provided on the board, wherein the pad is provided with a depression or the pad is formed in an annular shape. 3. A printed circuit board in which solder bumps are formed on pads provided on a board, wherein the thickness of the solder resist formed on the board at the periphery of the pad is greater than the thickness of the pad. And a recess provided at a location corresponding to the pad. 4. The method for manufacturing a printed circuit board according to claim 1, wherein after positioning a solder ball at a position corresponding to the pad, the solder ball is melted to form a solder bump. A method for manufacturing a printed circuit board, comprising: forming a printed circuit board on a surface of a printed circuit board;