JPH10335517A - Bga type package board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a solder ball from having cavities formed therein or from dispersing, by coating some portions of a conductor layer with degassing films expanding from the outer peripheral portions of the conductor layer to a through-hole. SOLUTION: In the peripheral edge portion of a through-hole 13 bored in a BGA type package board 10 which is present on the surface of the package board 10, a conductor layer 14b for the connection of a solder ball is formed to provide thereon, e.g. a plating film 15. Then, the whole of the conductor layer 14b and the plating film 15 is coated with a solder resist layer 12. Next, after applying a predetermined treatment process to the solder resist layer 12, degassing films, i.e., resist layers 19 are formed in some portions of the conductor layer 14b. Each resist layer 19 is provided in the portion expanded aiming at the center of the through-hole 13 from the outer peripheral portion of the conductor layer 14 to its inner peripheral portion. The resist layers 19 constitute together a crossed planar form, expanding in four ways or a Y-shaped planar form, expanding in three ways.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ball grid array type package substrate (hereinafter referred to as a BGA type package substrate).
It relates to a GA type package substrate.

[0002]

2. Description of the Related Art In order to protect a semiconductor element and at the same time connect with a wiring formed on a motherboard, the semiconductor element is mounted on various package substrates. As such a package substrate, for example, QFP (Quad Fl
at Package), a PGA (Pin Grid Array) type package substrate, and the like. These package substrates are actively used at present. However, with the recent increase in the degree of integration of semiconductor devices, the number of connection terminals formed on the semiconductor device has been rapidly increasing. Accordingly, it is necessary to increase the number of connection terminals of the package substrate for connection with the motherboard. However, in the above-mentioned QFP and PGA type package substrates, there is a limit in increasing the number of connection terminals due to its structure. is there.

[0003] Recently, BGA has attracted attention.
It is a mold package substrate. FIG. 5 shows a plastic B
It is the elements on larger scale which showed an example of GA type package substrate typically.

In FIG. 1, a BGA type package substrate 30 is composed of a plastic substrate 31, on which a semiconductor element 32 is connected and fixed by die bonding. Conductor layers 34a and 34b made of copper (Cu) or the like are formed on both main surfaces of the plastic substrate 31, and the conductor layers 34a and 34b
Is the conductor layer 34 formed on the wall surface of the hollow through hole 33
c. These are collectively referred to as a conductor layer 34. On the motherboard connection surface 38, the conductor layer 34b existing around the through hole 33 and the electrode pad 35 formed near the conductor layer 34b are connected, and the solder ball 36 is connected to the electrode pad 35. I have. The electrode pad of the semiconductor element 32 mounted on the semiconductor element mounting surface 37
The conductor layer 34a (not shown) is connected to the conductor layer 34a by wire bonding using a wire 39.

In order to make connection with the motherboard, for example, a solder ball 36 connected to the electrode pad 35 of the BGA type package substrate 30 is connected to the motherboard, and directly above a connection terminal formed for the solder ball. The solder balls 36 are reflowed.

However, in the BGA type package substrate 30, since the electrode pads 35 for connecting the solder balls 36 are formed at positions different from the through holes 33, the area of the package substrate must be increased accordingly. As a result, there is a problem that the package substrate becomes large.

[0007]

As a means for reducing the size of the package substrate, the present applicant has previously connected a solder ball directly below a hollow through-hole formed in a plastic substrate. A BGA type package substrate was proposed (Japanese Patent Application No. 8-64977).

FIG. 6A is a partially enlarged sectional view schematically showing a BGA type package substrate having the above structure, and FIG. 6B is a bottom view thereof. In the figure, on a BGA type package substrate 40, conductor layers 14a and 14b are formed on both main surfaces of a plastic substrate 11, and these conductor layers 14a and 14b are connected by a conductor layer 14c formed on the wall surface of the through hole 13. ing. These are collectively referred to as conductor layers 14. In addition, the semiconductor element mounting surface 17 is almost entirely covered with the solder resist layer 12 to protect the conductor layer 14a, and the motherboard connection surface 18 also except for the periphery of the portion where the through hole 13 is formed, Similarly, it is covered with a solder resist layer 12. Therefore, the through holes in the semiconductor element mounting surface 17
13 is closed by the solder resist layer 12, but the other portions (most of the through holes 13 and the periphery of the through holes 13 on the motherboard connection surface 18) have the solder resist layer 12 removed. Further, a plating film 15 (Ni layer or Ni layer and Au layer) is formed on the conductor layer 14c on the wall surface of the through hole 13 not covered with the solder resist layer 12 and the conductor layer 14b on the motherboard connection surface 18. Have been. The solder ball 16 is connected directly below the through hole 13.

The connection method with the motherboard is almost the same as that of the BGA type package substrate 30 shown in FIG.
In the BGA type package substrate 40, since the solder balls 16 are connected immediately below the through holes 13, an area for forming the electrode pads 35 is required as in the BGA type package substrate 30 shown in FIG. And the size of the package substrate can be reduced accordingly.

FIGS. 7A to 7D show the BGA shown in FIG.
FIG. 6 is a partially enlarged cross-sectional view schematically showing a part of the manufacturing process of the mold package substrate 40. As shown in FIG. 7A, after the conductor layer 14 is formed on both the main surfaces 17, 18 and the through hole 13 of the plastic substrate 11 in which the hollow through hole 13 is formed, a mask is formed on the conductor layer 14. 27, and then subjected to an etching process to form the conductor layer 14 (14a, 14b,
14c) is formed.

Next, as shown in FIG.
(14a, 14b, 14c) formed plastic substrate 11
An ultraviolet-curable solder resist layer 12 is formed on both principal surfaces of. At this time, the inside of the through hole 13 is also filled with the solder resist layer 12. Then, both main surfaces of the plastic 11 substrate are irradiated with ultraviolet rays 21 via the mask 20, and then subjected to a development process, so that the solder resist layer 12 around the through holes 13 inside the through holes 13 and the motherboard mounting surface 18 is formed. It is removed (see FIG. 7 (c)).

As shown in FIG. 7 (d), the conductor layers 14b and 14c exposed by the development process are subjected to a plating process so that a plating film is formed on the inner wall of the through hole 13 and around the through hole 13 on the mother board mounting surface 18. Form 15.

After that, immediately below the through hole 13 (the conductor layer
By bonding the solder balls 16 and performing reflow, the manufacturing of the BGA type package substrate 40 shown in FIG. 6 is completed.

However, such a BGA type package substrate 40
In the above, at the time of reflow of the solder ball 16 described above,
As shown in FIG. 8, there is a problem that a cavity 16a is formed inside the solder ball 16, or the solder ball 16 ruptures and is lost. It is considered that this is because the water remaining in the through-hole 13 becomes steam due to heating during reflow, and the pressure inside the through-hole 13 increases.

Here, an object of the present invention is to provide a BGA that does not form a cavity inside the solder ball or lose the solder ball even when the solder ball adhered to the conductor layer is reflowed immediately below the through hole. To provide a mold package substrate.

[0016]

These problems cannot be solved only by increasing the baking time or increasing the temperature, but rather prolong the baking lead time and increase the cost. .

Here, in order to achieve the above object, a BGA type package substrate according to the present invention has a hollow through-hole, one end of which is closed by a solder resist layer, and the through-hole is opened. In a BGA type package substrate in which a conductor layer for solder ball connection is formed around the other end of the hole, a part of the conductor layer is covered with a degassing film extending from an outer peripheral portion of the conductor layer to a through hole. It is characterized by.

Here, the present invention is as follows. (1) A ball grid array type package substrate in which a solder ball connection conductor layer is formed on a peripheral portion of a through hole on a package substrate surface, wherein the solder ball connection conductor is provided on the solder ball connection conductor layer. A ball grid array type package substrate, comprising at least two gas vent coatings extending from a peripheral portion to an inner peripheral portion of the layer.

(2) A ball grid array type package substrate in which a solder ball connection conductor layer is formed on the periphery of a through hole on a package substrate surface, wherein a part of the solder ball connection conductor layer is vented. A ball grid array type, wherein the degassing film is provided in a cross shape extending in four directions from the center of the through hole or in a Y shape extending in three directions. Package substrate.

(3) The ball grid array type according to the above (1) or (2), wherein the degassing film is provided on the surface of the conductor layer for solder ball connection in a convex shape. Package substrate.

(4) The ball grid array type package substrate according to the above (1) or (2), wherein the degassing film and the surface of the solder ball connecting conductor layer are flush with each other. .

(5) A ball grid array type package substrate in which a conductor layer for connecting a solder ball is formed at a peripheral portion of a via hole of the package substrate, wherein a part of the conductor layer for connecting a solder ball is a degassing film. A ball grid array type package substrate which is coated.

(6) The ball grid array type package substrate according to any one of (1) to (5), wherein the degassing film is a resin film.

Therefore, according to the BGA type package substrate of the present invention, a part of the conductor layer for connecting the solder balls is covered with the degassing film having poor wettability with the solder, so that the solder balls are connected to the conductor. When reflow is performed after bonding to the layer, even if water vapor or the like is generated in the through hole, the water vapor passes through the space between the degassing film and the solder ball and escapes to the outside, forming a cavity in the solder ball. And the solder balls do not rupture.
As the reflow proceeds, soldering of the solder ball and the conductor layer is performed, and soldering is performed including the portion of the degassing film.

Further, according to the present invention, although such a film having poor solder wettability is partially provided on the conductor layer originally provided for improving the bonding with the solder ball, the connection strength is reduced. According to the present invention, such a strength deterioration was not substantially observed, and gas in the through hole could be effectively escaped, although it was thought that the gas would deteriorate. Such effects are unexpected.

Further, the method of manufacturing a BGA type package substrate according to the present invention is characterized in that both sides of a BGA type package substrate having a conductor layer for solder ball connection formed around one end of a hollow through hole, A solder resist layer forming step of forming a solder resist layer in a portion including the through hole and the conductor layer, and using a photolithography technique, the solder resist layer on the conductor layer is removed so as to remain as a gas release resist layer. And a solder resist layer removing step.

Therefore, according to such a manufacturing method, in the conventional step of partially removing the photoresist layer, the shape of the mask when irradiating ultraviolet rays is changed, so that the photoresist layer can be relatively easily formed on the conductive layer. A degassing resist layer can be formed, and by using this as a degassing film during reflow, degassing is facilitated and solder balls can be satisfactorily connected to the conductor layer.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a BGA type package substrate according to the present invention will be described more specifically with reference to the accompanying drawings. In the following, the same members are denoted by the same reference numerals.

In the present invention, the type of the target BGA type package substrate is not particularly limited, but the hollow through hole is usually formed of plastic. Therefore, the plastic BGA type package substrate shown in FIG. 7 will be described below as an example. For convenience of description, the present invention will be described by taking a through hole penetrating the upper and lower surfaces of a plastic substrate, that is, a through hole as an example, but the present invention can be similarly applied to a via hole penetrating between wiring layers of a multilayer substrate. It is.

FIGS. 1A and 2A are partially enlarged sectional views schematically showing a part of a BGA type package substrate according to the present invention, and FIGS. 1B and 2B. Is a bottom view thereof.

In the figure, a BGA type package substrate 10 according to the present invention has a conventional BGA shown in FIG. 7 except that an X-shaped and a Y-shaped degassing film are formed on the exposed conductor layer 14b. Since the configuration is the same as that of the mold package substrate 40, a detailed description thereof is omitted here.

Here, the “gas release film” used in the present invention is a film that exhibits an action of escaping gas generated at the time of reflow, and is functionally insufficient in wettability with solder. There is no particular limitation as long as it is a film that can secure a gas release space by utilizing the repulsion with the molten solder, but in the following example, the case of forming with a UV-curable solder resist layer will be described.

That is, according to the present invention, the solder ball connection conductor layer 14b is formed on the periphery of the through hole 13 provided in the BGA type package substrate 10 on the package substrate surface.
Is formed, and in the illustrated example, a plating film 15 such as Ni or Au is provided thereon. This plating film 15
Means that when Cu is used for the conductor layer 14b, solder Sn (tin)
It is necessary to form an intermetallic compound called CuSn in order to prevent the interface from becoming brittle.However, the use of other conductive materials does not generate such a brittle reactant. If so, there is no need to provide the plating film 15 in particular. The conductor layer 14b and the plating film 15 are entirely covered with the solder resist layer 12.

[0034] Solder resist layer used in the present invention
Examples of 12 include melamine, epoxy, acrylic, polystyrene, polyimide, polyurethane, silicone, and the like. Then, the solder resist layer 12 is subjected to ultraviolet irradiation and development processing steps to form the conductor layer 14.
A degassing film, that is, a resist layer 19 is formed on a part of b. The resist layer 19 is formed as shown in FIG.
In (b), as shown by a white area, the portion is provided from the outer peripheral portion of the conductor layer 14b to the inner peripheral portion of the conductor layer 14b toward the center of the through hole 13.
In the case of FIG. 1 (b), it has a cross shape extending in four directions from the center of the through hole 13, and in the case of FIG. 2 (b), it has a Y shape which also extends in three directions from the center of the through hole 13.

At this time, the resist layer 19 has a convex shape, and when the solder ball 16 is placed thereon, a groove is formed between the resist ball 19 and the solder ball 16, which further enlarges the gas vent space. Effective degassing is possible.

Alternatively, in another embodiment, a conductive material such as a solder paste may be embedded around the convex resist layer 19 by means of a stalline printing or may be made the same surface by electroless plating. . From the viewpoint of the stability of holding the solder balls, it is preferable that the surfaces are the same.

The convex degassing resist layer 19
If the thickness of the solder ball is too large, when the solder ball melts during the solder reflow, a large amount of the solder ball melted into the groove may fall and the shape of the ball after the reflow may greatly change.

Therefore, preferably, the resist layer
When the thickness of 19 increases to, for example, 40 μm or more, the surface is made the same as described above. Of course, even in such a case, a convex resist layer may be used if there is no particular problem.

In addition, the formation and material of the gas release film may be varied in many ways as long as the function of gas release defined in the present invention is exhibited. For example, a lithography method using a dry film may be used. In the case of forming a degassing film, or in the shape of a cross or a Y-shape, the convex resist layer 19 has a shape in which four or three resist layers 19 are appropriately arranged on the periphery of the through hole. If there is,
X-shaped, T-shaped and the like are also within the scope of the present invention.

Next, a method of manufacturing the BGA type package substrate 10 according to the present invention will be described. First, FIG.
After a conductor layer 14 having a predetermined pattern is formed on the plastic substrate 11 and the inner wall of the through hole 13 in the same manner as the method shown in FIG. 1A, an ultraviolet-curable solder resist layer 12 is formed on both main surfaces. At this time, the inside of the through hole 13 is also filled with the solder resist layer 12.

FIGS. 3A and 4A are partially enlarged cross-sectional views schematically showing a state where the plastic substrate 11 on which the solder resist layer 12 is formed is irradiated with ultraviolet rays. 4 (b) and FIG. 4 (b) are bottom views showing examples in which four and three degassing resist layers 19 are provided, respectively.

As shown in FIGS. 3 (a) and 4 (a),
The solder resist layers 12 provided on both main surfaces of the plastic substrate 11 are irradiated with ultraviolet rays 21.
When irradiating the ultraviolet rays on the side of the mask 18, the mask (shaded portion) shown in FIG. 3B and FIG. Irradiation of ultraviolet rays 21 is performed on the solder resist layer 12. Thereafter, when a developing process is performed, the inside and the surrounding portion of the through-hole 13 not irradiated with the ultraviolet rays are dissolved and removed, and on the conductor layer 14b, a degassing resist layer 19 (see FIG. 3 (b) and FIG. 4 (b) only) remain.

Thereafter, as shown in FIG. 1 and FIG. 2, a plating film 15 is formed by performing a plating process, and then a solder ball 16 is connected to obtain a BGA type package substrate 10 according to the present invention. Can be

In this BGA type package substrate 10, a gas release resist layer 19 is interposed between the conductor layer 14b (plating film 15) and the solder ball 16, and the gas release resist layer 19 is The wettability with 16 is not good. Therefore, when the solder ball 16 reflows, a gap is formed between the degassing resist layer 19 and the solder ball 16, and a gas such as water vapor escapes through the gap. Therefore, when the solder balls 16 reflow,
A cavity 16a is formed inside or a solder ball
There is no inconvenience that 16 will burst and be lost.

As described above, according to the present invention, the width of the gas release resist layer 19 can increase the adhesive strength between the conductor layer 14b and the solder ball 16 as long as the width through which the gas can escape during reflow of the solder ball 16 can be ensured. It is preferable that the width is as narrow as possible, and in practice, it is preferably about 30 to 40 μm. In addition, the height of the gas release resist layer 19 is determined by the solder ball 16 and the conductor layer.
Considering the adhesive strength to 14b, it is better to be as low as possible.

Further, in the illustrated example, three or four gas release resist layers 19 are provided. However, if two or more gas release resist layers 19 can be sufficiently degassed and the solder balls can be stably placed, it is particularly preferable. No restrictions. In a preferred embodiment,
It is preferable to provide three or four gas release resist layers 19.

In general, in the case of two stripes, the ball does not ride well on the center, so that the ball does not stick well. In addition, for example, the reflow time is about 4.5 minutes, and the temperature is raised at 50 ° C / min.
When reflow is required in a short time, such as when heating to 0 to 230 ° C, the solder does not melt well unless the ball is at the center, and the melted solder is applied to places where the solder wettability is poor Therefore, the joining strength is reduced. However, even in the case of two lines, such a problem can be partially solved if the same surface is formed by applying a solder paste, for example. If the number is five or more, the bonding area is reduced, and the strength may be reduced, which is not preferable.

Here, the embodiment of the present invention is as follows. (1) A ball grid array type package substrate in which a conductor layer for solder ball connection is formed on a peripheral portion of a through hole on a surface of a package substrate, and a part of the conductor layer for solder ball connection is a degassing film. A ball grid array type package substrate which is coated.

(2) The ball grid array type package substrate according to the above (1), wherein the degassing film is a resin film. (3) The ball grid array type package substrate according to the above (1) or (2), wherein the through hole is a hollow via hole.

(4) The above-mentioned (1) to (3), wherein the degassing film is provided on a portion from the outer peripheral portion to the inner peripheral portion of the solder ball connection conductor layer. A ball grid array type package substrate according to any one of the above.

(5) The above-mentioned (4), wherein the degassing film is provided in a cross shape extending in four directions from the center of the through hole or in a Y shape extending in three directions. Ball grid array type package substrate.

(6) The ball grid according to any one of (1) to (5), wherein the degassing film is provided on the surface of the solder ball connecting conductor layer in a convex shape. Array type package substrate.

(7) The ball grid array type according to any one of (1) to (5), wherein the degassing film and the surface of the solder ball connecting conductor layer are on the same plane. Package substrate.

(8) On both surfaces of a substrate having a hollow through hole formed therein and a conductor layer for solder ball connection formed around the other end of the through hole, the through hole and the conductor layer In the portion including, a solder resist layer forming step of forming a solder resist layer, and using a photolithography technique, a solder resist layer removing step of removing the solder resist layer on the conductor layer so that a gas release resist layer remains A method of manufacturing a ball grid array type package substrate, comprising:

[0055]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a BGA type package substrate and a method of manufacturing the same according to the present invention will be described below. As a comparative example, a BGA type package substrate shown in FIG. 6 was manufactured and evaluated.

<Conditions Common to Examples and Comparative Examples> Plastic substrate 11 Type of plastic: BT (bismaleimide / triazine) resin Length: about 333 mm, width: about 250 mm Diameter of through hole 13: 150 μm Conductive layer 14 Metal constituting the conductor layers 14a, 14b, 14c: Cu Thickness of the conductor layers 14a, 14b: 10 μm Thickness of the Ni / Au plating film 15: 5.5 μm Number of samples: In the embodiment, the resist layer shape X for degassing is used. Shape, shape of resist layer for degassing Y shape, both comparative examples
10 pieces.

<Conditions in Example> Manufacturing of BGA type package substrate 10 (FIGS. 1 and 2) Solder resist layer 12 [Material: Taiyo Ink Manufacturing Co., Ltd.]
AUS5.

Thickness T: 50 μm Outgassing resist layer 19 Thickness t: 15 μm, width d: 30 μm, length 1: 75 μm Solder paste is applied by screen printing between the outgassing resist layers to make the same surface. Flattened and not flattened (thickness of resist layer 19 when flattened: 40 μm) Diameter of solder ball 16: 760 μm Number of solder balls 16 connected directly below through hole 13: 40
0 pieces.

<Conditions for Comparative Example> Production of BGA Type Package Substrate 40 (FIG. 6) The production was carried out under the same conditions as in Example 1 except that the degassing resist layer 19 was not formed.

<Evaluation Method and Evaluation Results> Evaluation method After bonding the solder balls 16 to the conductor layer 16b,
BGA type package substrate 1 under the condition of 60 ℃ and relative humidity 60%
0 and 40 were left for 10 days, and then reflowed at 210 ° C. Then, the ratio of the solder ball 16 in which a cavity was formed at the time of reflow and the solder ball 16 ruptured was determined for all the solder balls 16 connected to the conductor layer 14b. Note that whether or not a cavity was formed in the solder ball 16 was visually determined.

Evaluation Results In the examples in which the shape of the gas release resist layer was a cross shape and a Y shape, both the case where the solder paste was applied between the gas release layers and the case where no solder paste was applied,
There were no voids formed in 16 or no ruptured solder balls 16, and the percentage of defective solder ball connections was 0%
Met. On the other hand, in the case of the comparative example, the defective ratio of the solder ball connection was 5 to 30%, and a considerable portion of the solder balls 16 had cavities 16a formed or burst when reflowed. Degassing resist layer thickness of 40
When the solder ball is flattened to μm, the shape deformation of the solder ball after reflow has a very small change in ball height (distance from the resist layer interface to the top of the solder ball).
It was found to have high reliability. The connection strengths of the solder balls were almost the same in both cases, and no practical problem occurred.

[0062]

As described above, according to the present invention, by providing a gas venting film on a conductor layer of a BGA type package substrate, solder rupture during solder ball reflow,
Eliminating the size of the ball has been eliminated, and the deformation of the ball during reflow can be suppressed.

[Brief description of the drawings]

FIG. 1A is a partially enlarged cross-sectional view schematically showing a part of a BGA type package substrate having a cross-shaped resist layer for degassing according to an embodiment of the present invention. 1
(B) is a bottom view thereof.

FIG. 2A is a partially enlarged cross-sectional view schematically showing a part of a BGA type package substrate having a Y-shaped degassing resist layer according to an embodiment of the present invention. 2
(B) is a bottom view thereof.

FIG. 3A is a partially enlarged view schematically showing a state in which a plastic substrate on which a solder resist layer is formed is irradiated with ultraviolet rays in the method of manufacturing the BGA type package substrate shown in FIG. 1; FIG. 3B is a cross-sectional view, and FIG.

FIG. 4A is a partially enlarged view schematically showing a state in which ultraviolet light is irradiated on a plastic substrate on which a solder resist layer is formed in the method of manufacturing the BGA type package substrate shown in FIG. 2; It is sectional drawing, FIG.4 (b) is the bottom view.

FIG. 5 is a partially enlarged sectional view schematically showing an example of a conventional plastic BGA type package substrate.

FIG. 6 (a) is a partially enlarged cross-sectional view schematically showing another conventional BGA type package substrate.
(B) is a partially enlarged bottom view thereof.

7A to 7D are partially enlarged cross-sectional views schematically showing a part of a manufacturing process of the BGA type package substrate shown in FIG.

FIG. 8 is a partially enlarged cross-sectional view showing a state where solder balls are formed at the time of solder ball reflow in a conventional BGA type package substrate.

Claims (6)

[Claims] 1. A ball grid array type package substrate in which a conductor layer for solder ball connection is formed on a peripheral portion of a through hole on a surface of a package substrate, wherein the solder ball connection is formed on the conductor layer for solder ball connection. A ball grid array type package substrate provided with at least two gas vent coatings extending from an outer peripheral portion to an inner peripheral portion of the conductor layer. 2. A ball grid array type package substrate in which a conductor layer for solder ball connection is formed on a peripheral portion of a through hole on a surface of a package substrate, wherein a part of the conductor layer for solder ball connection is used for degassing. The gas venting film has a cross-shaped shape extending in four directions from the center of the through hole or a Y-shaped material extending in three directions.
A ball grid array type package substrate provided in a character shape. 3. The ball grid array type package substrate according to claim 1, wherein the degassing film is provided on the surface of the conductor layer for solder ball connection in a convex shape. 4. The ball grid array type package substrate according to claim 1, wherein the degassing film and the surface of the solder ball connecting conductor layer are flush with each other. 5. A ball grid array type package substrate in which a conductor layer for connecting a solder ball is formed on a peripheral portion of a via hole of a package substrate, wherein a part of the conductor layer for connecting a solder ball is covered with a degassing film. A ball grid array type package substrate characterized in that: 6. The ball grid array type package substrate according to claim 1, wherein said degassing film is a resin film.