JPH1065043A - Ball grid array type package substrate and method of manufacturing the same - Google Patents

Abstract

(57) [Problem] To provide a conventional BGA type package substrate,
Solder balls were adhered to the conductor layer formed around the through hole so as to cover the through hole, and then reflowed and connected to the conductor layer.However, gas such as water vapor was generated inside the through hole during reflow. Then, a cavity is formed inside the solder ball due to this gas,
Alternatively, there has been a problem that the solder ball is ruptured and lost, and connection failure occurs in connection of the solder ball to the conductor layer. SOLUTION: A hollow through hole 13 is formed,
In the BGA type package substrate 10 in which one end of the through hole 13 is closed by the solder resist layer 12 and a conductor layer 14b for solder ball connection is formed around the other end of the opened through hole 13, a part of the conductor layer 14b is formed. Then, the conductor layer 14b is covered with a gas release resist layer 19 extending from the periphery to the through hole 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a ball grid array type package substrate (hereinafter, referred to as a BGA type package substrate) and a method of manufacturing the same, and more particularly, to a BGA type package substrate on which a semiconductor element is mounted and a method of manufacturing the same. .

[0002]

2. Description of the Related Art In order to protect a semiconductor device and at the same time to connect with a wiring formed on a motherboard, the semiconductor device is mounted on various packages. As the package, for example, QFP (Quad Flat Package),
PGA (Pin Grid Array) type packages and the like are listed, and these packages are currently being used actively. 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. Therefore, it is necessary to increase the number of connection terminals of the package for connection with the motherboard.
In P and PGA type packages, there is a limit in increasing the number of connection terminals due to its structure.

[0003] Recently, BGA has attracted attention.
It is a mold package substrate. FIG. 6 shows plastic B
It is the elements on larger scale which showed an example of GA type package substrate typically.

In this BGA type package substrate 30, a semiconductor element 32 is connected and fixed to a plastic substrate 31 by die bonding. A conductor layer 34 made of copper (Cu) or the like is provided on both main surfaces of the plastic substrate 31.
a and 34b are formed, and the conductor layers 34a and 34b are formed on the wall of the hollow through hole 33.
c. Also, motherboard connection surface 3
8 includes a conductor layer 34 b existing around the through hole 33.
And an electrode pad 3 formed near the conductor layer 34b.
5 is connected, and a solder ball 36 is connected to the electrode pad 35. Further, an electrode pad (not shown) of the semiconductor element 32 mounted on the semiconductor element mounting surface 37 is connected to the conductor layer 34 a by wire bonding using a wire 39.

For connection with a motherboard, for example, the electrode pads 35 of the BGA type package substrate 30
Is positioned so that the solder ball 36 connected to the solder ball 36 is directly above a connection terminal (not shown) formed on the motherboard, and the solder ball 36 is reflowed.

However, the BGA type package substrate 30
In (2), 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, and the size of the package substrate increases. there were.

Accordingly, the present applicants have previously proposed a BGA type package substrate in which solder balls are connected directly below hollow through holes formed in a plastic substrate as means for reducing the size of a package. (Japanese Patent Application No. 8
-64977).

FIG. 7A is a partially enlarged sectional view schematically showing a BGA type package substrate having the above structure, and FIG. 7B is a bottom view thereof.

In the BGA type package substrate 40, the conductor layers 14a, 1
4b are formed, and these conductor layers 14a and 14b are connected by a conductor layer 14c formed on the wall surface of the through hole 13. The semiconductor element mounting surface 17 is
Almost the entire surface is covered with the solder resist layer 12 to protect the a and 14b, and the motherboard connection surface 18 is also
Except around the part where the through hole 13 is formed,
Similarly, it is covered with a solder resist layer 12. Therefore, the through hole 13 on the semiconductor element mounting surface 17 is closed by the solder resist layer 12, but the other portions (most of the through hole 13 and the periphery of the through hole 13 on the mother board connection surface 18) are solder resist. Layer 12 has been removed. Further, a plating film 15 (Ni layer, or Ni layer and Au layer) is formed on the conductor layer 14 c on the wall surface of the through hole 13 not covered with the solder resist layer 12 and the conductor layer 14 b on the motherboard connection surface 18.
Are formed. A 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, a region for forming the electrode pads 35 like the BGA type package substrate 30 shown in FIG. Is not required, and the size of the package substrate can be reduced.

[0012]

FIGS. 8A to 8D are partially enlarged sectional views schematically showing a part of the manufacturing process of the BGA type package substrate 40 shown in FIG.

After the conductor layer 14 is formed on both main surfaces of the plastic substrate 11 having the hollow through-holes 13 formed therein and the through-holes 13, a mask 27 is formed on the conductor layer 14 (FIG. 8A). Then, an etching process is applied to the conductor layer 14 (14a, 14b, 14c) having a predetermined pattern.
To form

Next, the conductor layers 14 (14a, 14b, 14
An ultraviolet-curable solder resist layer 12 is formed on both main surfaces of the plastic substrate 11 on which c) is formed. On this occasion,
The inside of the through hole 13 is also filled with the solder resist layer 12. Next, both main surfaces of the plastic substrate 11 are irradiated with ultraviolet rays 21 via the mask 20 (FIG. 8B), and then subjected to a development process, whereby the inside of the through holes 13 and the through holes 13 in the motherboard mounting surface 18 are formed. The surrounding solder resist layer 12 is removed (FIG. 8C).

The conductor layer 14 exposed by the development process
A plating process is performed on b and 14c to form a plating film 15 on the inner wall of the through hole 13 and around the through hole 13 on the motherboard mounting surface 18 (FIG. 8D).

Then, immediately below the through hole 13 (the conductor layer 1)
By bonding the solder balls 16 and performing reflow to 4b), the manufacture of the BGA type package substrate 40 shown in FIG. 7 is completed.

However, the conventional BGA type package substrate 4
In FIG. 9, when the solder ball 16 is reflowed, as shown in FIG.
There has been a problem that the solder balls 6a are formed or the solder balls 16 burst and are lost. This is because
It is considered that the moisture remaining in the through hole 13 becomes steam due to heating during reflow, and the pressure inside the through hole 13 increases.

The present invention has been made in view of the above problems, and even when a solder ball bonded (to a conductor layer) immediately below a through hole is reflowed, a cavity is formed inside the solder ball or the solder ball is formed. It is an object of the present invention to provide a BGA type package substrate which does not dissipate and a method of manufacturing the same.

[0019]

In order to achieve the above object, a BGA type package substrate (1) according to the present invention has a hollow through hole, and one end of the through hole has a solder resist layer. In a BGA type package substrate in which a conductor layer for solder ball connection is formed around the other end of the through hole which has been closed and opened, a part of the conductor layer is formed from the periphery of the conductor layer to the through hole. It is characterized by being covered with a resist layer for gas release.

According to the BGA type package substrate (1), since a part of the solder ball connecting conductor layer is covered with the degassing resist layer having poor wettability with the solder, the solder ball can be removed. When reflow is performed after bonding to the conductor layer, even if water vapor or the like is generated in the through hole, the water vapor passes through between the periphery of the degassing resist layer and the solder ball, and escapes to the outside, and enters into the solder ball. No cavities are formed and no solder balls burst. Therefore, it is possible to provide a BGA type package substrate in which the solder balls are satisfactorily connected to the conductor layer.

Further, in the BGA type package substrate (2) according to the present invention, a hollow through-hole is formed, one end of the through-hole is closed by a solder resist layer, and the other end of the opened through-hole is formed around the other end. In the BGA type package substrate in which a conductor layer for solder ball connection is formed, a notch for venting from a periphery of the conductor layer to the through hole is formed in a part of the conductor layer. Features.

According to the BGA type package substrate (2), a cutout portion for venting gas is formed in a part of the conductor layer for solder ball connection, and the substrate having poor wettability with solder is exposed. Therefore, when the solder ball is adhered to the conductor layer and then reflowed, even if steam or the like is generated in the through hole, the steam escapes to the outside through the gas vent cutout portion, and a cavity is formed in the solder ball. Is formed,
The solder balls do not burst. Therefore, the BGA in which the solder ball is connected to the conductor layer satisfactorily
It can be a mold package substrate.

Further, according to the method (1) for manufacturing a BGA type package substrate according to the present invention, in the method for manufacturing the BGA type package substrate (1), a hollow through hole is formed, and the other end of the through hole is formed. A solder resist layer forming step of forming a solder resist layer on both surfaces of the substrate on which a conductor layer for solder ball connection is formed, and including the through hole and the conductor layer, and a photolithography method. A solder resist layer removing step of removing the solder resist layer on the conductor layer so that only the gas release resist layer remains.

According to the manufacturing method (1) of the BGA type package substrate, in the conventional step of partially removing the photoresist layer, the shape of the mask when irradiating ultraviolet rays is changed, so that the method is relatively easy. A gas release resist layer can be easily formed on the conductor layer, and a solder ball can be favorably connected to the conductor layer.

In the method (2) for manufacturing a BGA type package substrate according to the present invention, the method for manufacturing a BGA type package substrate (2) is such that a hollow through hole is formed and includes a periphery of the through hole. The method includes a step of performing an etching process on the conductor layer so that the gas vent cutout is formed on the substrate having the conductor layer formed on at least one main surface.

According to the manufacturing method (2) of the BGA type package substrate, in the conventional patterning step of etching the conductor layer, the shape of the mask is changed to relatively easily connect the solder ball. A notch for venting can be formed in the conductor layer,
Solder balls can be satisfactorily connected to the conductor layer.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a BGA type package substrate according to the present invention will be described below with reference to the drawings.

In the BGA-type package substrate according to the embodiment, the type of the target BGA-type package substrate is not particularly limited, but usually, a hollow through hole is formed of plastic. It is.
Therefore, hereinafter, the same type as the plastic BGA type package substrate shown in FIG. 7 will be described as an example.

FIG. 1A is a partially enlarged sectional view schematically showing a part of a BGA type package substrate according to the embodiment, and FIG. 1B is a bottom view thereof.

The BGA type package substrate 10 according to the present embodiment is shown in FIG. 7 except that a strip-shaped degassing resist layer 19 is coated and formed on a part of the exposed conductor layer 14b. Conventional BGA type package substrate 4
0, the detailed description is omitted here.

In order to manufacture the BGA type package substrate 10, a conductor layer 14 having a predetermined pattern is formed on the plastic substrate 11 and on the inner wall of the through hole 13 in the same manner as shown in FIG. An ultraviolet-curable solder resist layer 12 is formed on the surface. At this time, the through hole 1
3 is also filled with a solder resist layer 12.

FIG. 2A is a partially enlarged sectional view schematically showing a state where the plastic substrate 11 on which the solder resist layer 12 is formed is irradiated with ultraviolet rays, and FIG. 2B is a bottom view thereof. is there.

As shown in FIG. 2, the plastic substrate 1
1 are irradiated with ultraviolet rays 21, but when the ultraviolet rays are irradiated on the motherboard connection surface 18 side, the through holes 13
The mask 20 having the shape shown in FIG. 2B is positioned on the solder resist 12 and irradiated with ultraviolet rays 21 so that ultraviolet rays are not irradiated around the solder resist 12. Thereafter, when a developing process is performed, the through holes 13 not irradiated with the ultraviolet rays are formed.
The inside and its surroundings are dissolved and removed, leaving only the gas release resist layer 19 (FIG. 1) on the conductor layer 14b. Thereafter, a plating process is performed to form a plating film 15 and solder balls 16 are connected to obtain a BGA type package substrate 10 having the configuration shown in FIG.

In this BGA type package substrate 10, the conductor layer 14b (plated film 15) and the solder ball 1
6, a gas release resist layer 19 is interposed,
The degassing resist layer 19 has poor wettability with the solder balls 16. Therefore, when the solder ball 16 is reflowed, the gas release resist layer 19 and the solder ball 16
And a gap is formed, and gas such as water vapor escapes through the gap. Therefore, there is no inconvenience that the cavity 16a is formed inside the solder ball 16 during the reflow of the solder ball 16, or the solder ball 16 is ruptured and lost.

FIG. 3A shows a BG according to another embodiment.
FIG. 2 is a partially enlarged cross-sectional view schematically illustrating an A-type package substrate, and FIG.

In the BGA type package substrate 25 according to the present embodiment, except that a strip-shaped gas vent cutout 26 is formed in a part of the exposed conductor layer 14b.
Since the configuration is the same as that of the conventional BGA type package substrate 40 shown in FIG. 7, the detailed description is omitted here.

In order to manufacture the BGA type package substrate 25, a mask 27 is formed on the conductor layer 14 formed on the plastic substrate 11 in a process corresponding to FIG.
Is formed and an etching process is performed to form the conductor layer 14 (14a, 14b, 14c) having a predetermined pattern, but the shape of the conductor layer 14b is different from the conventional case.

FIG. 4A is a partially enlarged sectional view schematically showing the plastic substrate 11 in which the mask 27 is formed on the conductor layer 14, and FIG. 4B is a bottom view thereof. FIG.
As shown in (b), the mask 27 is substantially circular, but a band-shaped notch 26 ′ is formed from a part of the outer periphery of the mask 27 to the through hole 13. Therefore, after the etching process, the conductor layer 14 is etched except for the portion covered with the mask 27, and as shown in FIG.
A substantially circular conductor layer 14b having a gas vent cutout 26 is formed around the periphery. After that, FIG.
The BGA type package substrate 25 is manufactured in the same manner as the method shown in FIG.

In the BGA type package substrate 25, the conductor layer 1b is formed on the circular conductor layer 14b (the plating film 15).
4b is not formed (notch portion 2 for degassing)
6), and the plastic substrate 1 having poor wettability with the solder ball 16 is formed in the cutout portion 26 for degassing.
1 is exposed. Therefore, when the solder ball 16 reflows, a gap 28 is formed between the exposed plastic substrate 11 and the solder ball 16, and a gas such as water vapor escapes through the gap 28. Therefore, when the solder ball 16 reflows, the cavity 16 is formed inside the solder ball 16.
There is no inconvenience that a is formed or the solder ball 16 ruptures and is lost.

FIG. 5 is a bottom view schematically showing the motherboard mounting surface 18 side of the BGA type package substrate 25. In this figure, the direction of the gas vent notch 26 formed in the conductor layer 14b is shown. ing.

After the BGA type package substrate 25 is mounted on a motherboard, the temperature rises due to heat generated from a semiconductor element when actually used, and the BGA type package substrate 25 tends to thermally expand. However, since the BGA type package substrate 25 is fixed to the motherboard by the solder balls 16 connected to the conductor layer 14b,
Thermal stress is generated in the solder balls 16. A gas vent cutout 26 is formed in the conductor layer 14b, and since the solder ball 16 is not bonded to the gas vent cutout 26, the bonding strength is weak at this portion, and the gas vent cutout is formed. Depending on the direction of the notch 26, the solder ball 16
May be separated from the conductor layer 14b by thermal stress.

However, in the present embodiment, as shown in FIG. 5, the longitudinal direction of the gas vent notch 26 extends from the center of the BGA type package substrate 25 to the through hole 1.
3 are formed so as to be perpendicular to the straight lines A and B drawn toward 3, the solder ball 16 has the smallest thermal stress, and the solder ball 16
There is no fear of peeling off from the conductor layer 14b. The width d ₂ (FIG. 3) of the gas vent cutout 26 is not limited as long as the width through which the gas escapes during reflow of the solder ball 16 can be secured.
It is better to be as narrow as possible to increase the adhesive strength with b.
Actually, it is preferably about 100 to 200 μm.

The degassing resist layer 19 (FIG. 1) formed on the BGA type package substrate 10 is exactly the same, and its longitudinal direction is the BGA type package substrate 1.
It is preferable that the direction be perpendicular to the straight line drawn from the center of 0 to the through hole 13, and the width d ₁ be 100 to 100.
It is preferably about 200 μm.

[0044]

Examples and Comparative Examples Hereinafter, examples of a BGA type package substrate and a method of manufacturing the same according to the present invention will be described. As a comparative example, a BGA type package substrate was manufactured by a conventional method and evaluated.

<Conditions Common to Examples and Comparative Examples> Plastic substrate 11 Type of plastic: BT (bismaleimide / triazine) resin Length: about 330 mm, width: about 250 mm, thickness: 0.3 m
m Diameter of through hole 13: 30 μm or more Conductive layer 14 Metal constituting conductive layers 14a, 14b, 14c: Cu Thickness of conductive layers 14a, 14b: 30 μm Thickness of Ni / Au plating film 15: 10 μm Number of samples: implemented Example and Comparative Example 10 <Conditions in Example 1> Production of BGA Type Package Substrate 10 (FIG. 1) Degassing resist layer 19 Thickness t ₁ : 50 μm, width d ₁ : 150 μm, length l ₁ :
0.3 mm Diameter of the solder balls 16: 0.7 mm Number of the solder balls 16 connected directly below the through holes 13: 300 <Conditions for the second embodiment> Manufacture of the BGA type package substrate 25 (FIG. 3) For degassing Notch 26 Width d ₂ : 150 μm, length l ₂ : 0.3 mm Diameter of solder ball 16: 0.7 mm Number of solder balls 16 connected directly below through hole 13: 300 <Conditions of Comparative Example 1 Production of BGA Type Package Substrate 40 (FIG. 7) Except that the outgassing resist layer 19 was not formed, it was produced under the same conditions as in Example 1.

<Evaluation Method and Evaluation Results> Evaluation Method After bonding the solder balls 16 to the conductor layer 14b, the BGA type package substrates 10, 25 and 40 were left for 10 days at a temperature of 30 ° C. and a relative humidity of 60%. And then 210
Reflowed at ℃. The solder ball 16 having a cavity formed during reflow, and the solder ball 16
Was determined for the total number of solder balls 16 connected to the conductor layer 14b. In addition, whether the cavity was formed in the solder ball 16 was visually determined.

Evaluation Results In Examples 1 and 2, none of the solder balls 16 had a cavity formed during reflow or the solder ball 16 ruptured, and the percentage of defective solder ball connections did not exist. Was 0%. On the other hand, in the case of Comparative Example 1, the defective rate of the solder ball connection was 5 to 30%, and a considerable proportion of the solder balls 16 had cavities 16a formed or burst when reflowed.

[Brief description of the drawings]

FIG. 1A is a partially enlarged sectional view schematically showing a part of a BGA type package substrate according to an embodiment of the present invention, and FIG. 1B is a bottom view thereof.

2A is a partially enlarged cross-sectional 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. And (b) is a bottom view thereof.

FIG. 3A is a partially enlarged cross-sectional view schematically showing a plastic BGA type package substrate according to another embodiment, and FIG. 3B is a bottom view thereof.

FIG. 4A is a partially enlarged cross-sectional view schematically showing a plastic substrate having a mask formed on a conductor layer in the method of manufacturing the BGA type package substrate shown in FIG. 3; Is a bottom view thereof.

FIG. 5 is a bottom view schematically showing a motherboard mounting surface side of a BGA type package substrate according to another embodiment.

FIG. 6 is a partially enlarged cross-sectional view schematically showing an example of a conventional plastic BGA type package substrate.

7A is a partially enlarged sectional view schematically showing another conventional BGA type package substrate, and FIG. 7B is a partially enlarged bottom view thereof.

FIGS. 8A to 8D are partially enlarged cross-sectional views schematically showing a part of the manufacturing process of the BGA type package substrate shown in FIG.

FIG. 9 is a partially enlarged cross-sectional view showing a state in which a cavity is formed in a solder ball during solder ball reflow in a conventional BGA type package substrate.

[Explanation of symbols]

 10, 25 BGA type package substrate base 12 Solder resist layer 13 Through hole 14 (14a, 14b, 14c) Conductive layer 19 Gas resist layer 26 Gas notch

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Toshihiko Kubo 4-33, Kitahama, Chuo-ku, Osaka City, Osaka Sumitomo Metal Industries, Ltd.

Claims (4)

[Claims] 1. A hollow through-hole is formed, and one end of the through-hole is closed by a solder resist layer.
In a ball grid array type package substrate in which a conductor layer for solder ball connection is formed around the other end of the opened through hole, a part of the conductor layer is formed by a gas reaching from the periphery of the conductor layer to the through hole. A ball grid array type package substrate, which is covered with a punching resist layer. 2. A hollow through hole is formed, and one end of the through hole is closed by a solder resist layer.
In a ball grid array type package substrate in which a conductor layer for solder ball connection is formed around the other end of the opened through hole, a gas reaching from the periphery of the conductor layer to the through hole is formed in a part of the conductor layer. A ball grid array type package substrate, wherein a cutout notch is formed. 3. 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, including the through-hole and the conductor layer. In part, 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 only the degassing resist layer remains 2. The method for manufacturing a ball grid array type package substrate according to claim 1, further comprising: 4. A conductor layer such that the gas vent cutout is formed in a substrate having a hollow through hole formed therein and a conductor layer formed on at least one main surface including the periphery of the through hole. 3. The method for manufacturing a ball grid array type package substrate according to claim 2, further comprising a step of performing an etching process on the substrate.