JPH11121520A - Ball grid array type semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the mounting reliability of a fine pitched BGA. SOLUTION: This semiconductor device has a structure, which has an external terminal 7 on one face of an electrically insulating substrate 3 having wiring patterns 2, and in which a reverse face of the electrically insulating substrate 3 is adhered to a face having an electrode terminal 8 of a semiconductor element 1. The electrode terminal 8 of the semiconductor element is connected electrically to the wiring patterns 2 of the electrically insulating substrate 3. The external terminal 7 has a structure in which a solder ball is connected to a mounting pad, and an electrically insulating sheet 6 having a through-hole in a solder ball mounting part is adhered to the surroundings of the mounting pad.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor device, and more particularly to a ball grid array (BGA) type semiconductor device.

[0002]

2. Description of the Related Art In recent years, the size and weight of semiconductor devices have been remarkably reduced. In particular, as a semiconductor device used for portable electronic equipment typified by a portable telephone, a device disclosed in Japanese Patent Application Laid-Open No. 7-32157 has been proposed. is there. This device is shown in FIG.
The external terminal 7 is provided on one surface of the electrically insulating substrate 3 having the wiring pattern 2 and the opposite surface is bonded to the surface having the electrode terminal 8 of the semiconductor element 1 as shown in FIG. 3 is electrically connected to the wiring pattern 2. 4 is a solder resist. Hereinafter, this device is called a fine pitch BGA. The external terminal of such a fine pitch BGA is formed by temporarily attaching a metal brazing material in the form of a sphere or a pellet to an electrode pad on an electrically insulating substrate, or by powdering the metal brazing material, mixing it with a flux to form a paste, The electrode pad is screen-printed and then reflowed at a temperature equal to or higher than the melting point of the metal brazing material to bond and form the electrode pad. Eutectic solder is often used as the metal brazing material, but there is also a material in which spherical high melting point solder is coated with eutectic solder, and a case in which spherical high melting point solder is bonded with eutectic solder paste.

Conventionally, semiconductor devices using spherical eutectic solder for external terminals include plastic ball grid arrays (hereinafter, P.BG) in addition to fine pitch BGA.
A). For P / BGA,
The external terminals have a relatively large pitch of 1 mm or 1.27 mm, and the spherical eutectic solder, which is an external terminal, has a diameter of 0.7 mm.
mm to 0.9 mm and the eutectic solder completely melts the external terminals during reflow, and performs self-alignment based on the surface tension of the solder. Not necessary, and after mounting, the thermal stress caused by the difference in the coefficient of thermal expansion between the P · BGA applied to the solder joint and the board is reduced by the P · BG
The smaller the gap with the A base, the smaller the gap.
In the case of GA, this gap is sufficient, and the substrate and P / BG
The thermal stress caused by the difference in the coefficient of thermal expansion from the base A can be sufficiently absorbed by the solder balls as the external terminals, and as a result, high reliability is obtained.

On the other hand, the pitch of the external terminals of the fine pitch BGA is 0.4 mm to 0.8 mm, and the size of the external terminals is 0.1 mm to 0.4 mm. Demanded to a high level. In addition, since the gap between the board after mounting and the fine pitch BGA base becomes narrow, and the outer size of the fine pitch BGA is close to the outer size of the semiconductor element, the overall thermal expansion coefficient of the silicon There is a problem that it is strongly affected, becomes smaller than P.BGA, a difference in thermal expansion coefficient with the substrate becomes large, and mounting reliability is reduced.

For this reason, as disclosed in Japanese Patent Application Laid-Open No. Hei 8-236654, a method of covering the peripheral portion of a solder ball with a resin before mounting, or a method of mounting a substrate with a fine pitch B
A method of filling a resin between GA bases (hereinafter referred to as an underfill) has been used to ensure mounting reliability.

[0006]

However, the first problem that arises with the above method is that disclosed in Japanese Patent Laid-Open No. Hei 8-2366.
As disclosed in Japanese Patent Application Publication No. 54-54, the method of covering the peripheral portion of the solder ball with a resin before mounting requires fine pitch B
This means that it is extremely difficult to cover the periphery of the GA solder ball with resin.

The reason is that the external terminal pitch of the fine pitch BGA is 0.4 mm to 0.8 mm, and the size of the solder ball as the external terminal is 0.1 mm to 0.4 m.
This is because, since the resin is small, sufficient accuracy cannot be obtained by potting or printing, and the resin adheres to portions to which the resin should not originally adhere, such as electrode pads on which solder balls are mounted.

The second problem is that when underfilling is performed, if a defect is found in the semiconductor device after mounting,
It is difficult to repair.

The reason is that, since the resin is bonded to the mounting board and the fine pitch BGA base, the resin must be removed first when repairing, but there is no method for removing the mounting board without damaging it. It is.

SUMMARY OF THE INVENTION It is an object of the present invention to prevent a solder ball as an external terminal from being destroyed due to the effect of thermal stress caused by a difference in thermal expansion coefficient between a substrate and a fine pitch BGA base after mounting a fine pitch BGA. Is to provide a ball grid array type semiconductor device capable of obtaining the following.

[0011]

In order to achieve the above object, in a ball grid array type semiconductor device according to the present invention, an external terminal is provided on one surface of an electric insulating substrate having a wiring pattern, and A ball grid array type semiconductor device, wherein the opposite surface is bonded to a surface having electrode terminals of the semiconductor element, and electrically connects the electrode terminals of the semiconductor element and the wiring pattern of the electrically insulating substrate. The external terminal has a structure in which a solder ball is connected to a mounting pad, and the electric insulating sheet has a through hole in a solder ball mounting portion and is attached to a periphery of the mounting pad.

The thickness of the electric insulating sheet is 50 μm.
That is all.

Further, the ball grid array type semiconductor device is mounted on a substrate, and the solder balls of the external terminals have a shape obtained by combining the shape of the through hole of the electric insulating sheet with the spherical solder formed on the mounting substrate. This increases the mounting height.

The ball grid array type semiconductor device is mounted on a substrate, and the solder balls of the external terminals reduce the stress applied to the electrode pads.

When a fine pitch BGA is mounted on a substrate by an electric insulating sheet having a through hole in a solder ball mounting portion attached to an external terminal mounting surface, the shape of the solder joint does not become a simple sphere. However, since it does not spread horizontally beyond the diameter of the through hole of the electric insulating sheet, the shape of the through hole and the shape of the spherical solder formed below the through hole (on the mounting board side) are combined, for example, a ball-like shape, and as a result, In the height direction, the distance between the substrate and the fine pitch BGA increases, and after mounting the fine pitch BGA,
Thermal stress caused by the difference in the coefficient of thermal expansion between the substrate and the fine pitch BGA substrate generated at the joint can be reduced.

[0016]

Next, an embodiment of the present invention will be described in detail with reference to FIG. In FIG. 1, the fine pitch BGA has external terminals 7 on one surface of an electrically insulating substrate 3 having a wiring pattern, and the opposite surface is bonded to a surface having electrodes 8 of the semiconductor element 1. The electrode 8 of the semiconductor element 1 and the wiring pattern 2 of the electrically insulating substrate 3 are electrically connected. In the present invention, the external terminals 7 are formed by connecting solder balls to mounting pads, and attaching an electric insulating sheet 6 having through holes in the solder ball mounting portion to the solder resist 4 around the mounting pads with an adhesive 5. Things.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a schematic sectional view showing an embodiment of the present invention.

In FIG. 1, although not shown, an adhesive of a polyimide-based thermoplastic resin is adhered to one surface of an electric insulating substrate 3 made of a polyimide resin. The thickness of the electrically insulating substrate 3 is 20 to 30 μm, and the thickness of the adhesive layer is 5 to 30 μm.
10 μm, and the thickness thereof is
It has almost the same thickness as.

The electrode 8 of the semiconductor element 1 and the electrically insulating substrate 3
And heat and a load and an ultrasonic wave are applied to the wiring pattern 2 to connect them, and then heat of about 300 ° C. and 1 kg / cm ^{2 are applied.}
The semiconductor element 1 and the electrically insulating substrate 3 are adhered by applying a load of. The wiring pattern is formed by etching a rolled copper foil and applying electrolytic copper plating. The solder resist 4 is coated with a polyimide resin having a thickness of 10 to 15 μm except for a portion (hereinafter referred to as an electrode pad) on which the external terminal 7 is mounted on the external terminal 7 side of the wiring pattern 2.

On the solder resist 4, an insulating sheet 6 made of a polyimide resin having an opening in the electrode pad portion larger than the electrode pad portion is adhered by using a thermosetting polyimide resin adhesive 5. The thickness of the insulating sheet 6 is 5
0 μm or more, particularly 95 to 105 μm, the size of the electrode pad is 175 to 185 μm, the opening diameter of the electrode pad portion of the insulating sheet 6 is 290 to 310 μm, and the thickness of the adhesive 5 is 10 to 20 μm. is there. When the insulating sheet 6 is bonded, the amount (thickness) of the adhesive 5 and the opening diameter of the electrode pad portion of the insulating sheet 6 with respect to the size of the electrode pad are determined so that the adhesive 5 does not flow into the electrode pad portion. I do.

Thereafter, a ball-shaped Sn is used as the external terminal 7.
The eutectic solder of Pb and Pb is placed on the electrode pad portion and connected by reflow.

Table 1 shows the results of a temperature cycle test in which the sample of this embodiment and the sample of the conventional example were mounted on a substrate. As can be seen from the results shown in Table 1, it can be seen that the application of this embodiment greatly extends the life and improves the mounting reliability.

[0024]

[Table 1]

The mounting substrate is a double-sided substrate made of glass cloth / epoxy resin called FR-4 and having a thickness of 0.8 mm. The electrode pad size is 0.3 mm in diameter, the pitch is 0.5 mm, and a certain amount of solder (equivalent to a ball having a diameter of 0.2 mm) is supplied to the electrode pads on the mounting board side as preliminary solder. The temperature cycle is performed at a temperature of -20C to 125C. In addition, as shown in FIG. 2, in order to prevent a gap (such as blister) from being generated between the solder resist 4 and the insulating sheet 6, a diameter of 0.05 to 0.1 mm other than the opening corresponding to the electrode pad for air release is used. Air vent through hole 12 can be provided.

According to the present invention, after mounting the fine pitch BGA, the mounting height with the mounting substrate can be increased.

FIG. 3 is a schematic cross-sectional view when the fine pitch BGA of this embodiment is mounted, and FIG. 4 is a schematic cross-sectional view when the conventional fine pitch BGA is mounted for comparison.

According to the present invention, as shown in FIG. 3, a fine pitch B is formed by using an electric insulating sheet 6 having a through hole in a solder ball mounting portion attached to a mounting surface of an external terminal 7.
When the GA is mounted on the board, the shape of the solder ball is
Since it does not become a simple sphere and does not spread laterally beyond the diameter of the through hole of the electric insulating sheet 6, the shape of the through hole and the spherical solder formed below the through hole (on the mounting substrate side) are like a ball. As a result, the distance between the mounting board 9 and the fine pitch BGA is increased as compared with the conventional example of FIG. H1 in FIG. 3 is the mounting height of the present embodiment, and h2 in FIG. 4 is the mounting height in the related art. While the mounting height h1 of the present embodiment is 0.17 mm, the mounting height h2 of the conventional example is
Is 0.09 mm.

According to the present invention, the fine pitch B
After mounting the GA, the thermal stress at the solder joint can be dispersed.

FIG. 5 is a schematic partial cross-sectional view when the fine pitch BGA of this embodiment is mounted, and FIG. 6 is a schematic partial cross-sectional view when the conventional fine pitch BGA is mounted for comparison.

Usually, the electrode pad size of the fine pitch BGA is smaller than the electrode size of the mounting board, and if it is damaged by thermal stress after mounting, it is the electrode pad section a on the fine pitch BGA side.

However, according to the present embodiment, since the insulating sheet 6 presses the middle of the solder ball of the external terminal, thermal stress also occurs in this portion b, and the heat applied to the electrode pad portion a on the fine pitch BGA side. This is because stress can be reduced. In the conventional example, a large thermal stress is applied to the electrode pad portion a because the middle of the solder joint is not pressed.

[0033]

As described above, according to the present invention, after mounting the fine pitch BGA on the mounting board, the reliability of the joint is improved, and it is sufficient to provide no underfill between the fine pitch BGA and the mounting board. Reliability can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment of the present invention.

FIG. 2 is a partially enlarged view showing another embodiment of the present invention.

FIG. 3 is a schematic sectional view for explaining the effect of the embodiment of the present invention.

FIG. 4 is a schematic sectional view of a conventional example shown for comparison.

FIG. 5 is a partially enlarged sectional view for explaining the effect of the embodiment of the present invention.

FIG. 6 is a partially enlarged sectional view of a conventional example shown for comparison.

FIG. 7 is a schematic sectional view showing a conventional example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor element 2 Wiring pattern 3 Electrical insulating substrate 4 Solder resist 5 Adhesive 6 Insulating sheet 7 External terminal 8 Electrode 9 Mounting substrate 10 Wiring pattern 11 Solder resist 12 Air vent through-hole h1, h2 Symbol indicating mounting height a, b Bonding Symbol indicating the location of the part d1, d2, d3 Symbol indicating the diameter of the joint

Claims (4)

[Claims] An electric insulating substrate having a wiring pattern has external terminals on one surface thereof, and an opposite surface of the electric insulating plate is bonded to a surface having electrode terminals of the semiconductor element, and is electrically connected to the electrode terminals of the semiconductor element. A ball grid array type semiconductor device electrically connecting a wiring pattern of a substrate, the device having an electric insulating sheet, external terminals having a structure in which solder balls are connected to mounting pads, A ball grid array type semiconductor device having a through hole in a solder ball mounting portion and attached to a periphery of a mounting pad. 2. The semiconductor device according to claim 1, wherein the thickness of the electric insulating sheet is 50 μm or more. 3. The ball grid array type semiconductor device according to claim 1, wherein the semiconductor device is mounted on a substrate, and the solder balls of the external terminals are formed of a through hole of an electric insulating sheet and a spherical solder formed on the mounting substrate. A ball grid array type semiconductor device characterized in that the height of the mounting is increased by adopting a shape combining the above. 4. The ball grid array type semiconductor device according to claim 1, wherein the ball is mounted on a substrate, and the solder ball of the external terminal reduces a stress applied to an electrode pad portion.・
Grid array type semiconductor device.