JP2555994B2 - Flip chip mounting method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flip chip mounting method for mounting a semiconductor element such as an LSI on a circuit board.

[0002]

2. Description of the Related Art In recent years, high-density mounting of simplified semiconductor elements has been increasing with the downsizing and cost reduction of electronic devices. There is a flip chip method as a method of mounting such a semiconductor element such as an LSI on a circuit board.

This is a method of connecting a semiconductor element having a plurality of bump electrodes to a circuit board by a face-down method.

FIG. 3 shows a sectional view of a flip-chip mounting structure in which the semiconductor element 6 is mounted on the circuit board 1 by a conventional method. Here, 7 is a bump electrode formed on the pad of the semiconductor element 6, and is connected to the mounting pad 3 on the circuit board 1. Reference numeral 4 denotes an adhesive for fixing the semiconductor element 6 and the circuit board 1 in a connected state, and a photo-curable or thermosetting resin is used.

A method of flip-chip mounting the semiconductor element 6 having the structure shown in FIG. 3 is disclosed in Japanese Patent Application Laid-Open No. 4-82241. That is, the adhesive resin 4 is applied by screen printing to a region on the circuit board 1 where the semiconductor element 6 is fixed (including the mounting pad 3 on the circuit board 1). As for the method of supplying the resin, a method of supplying the resin only to the center of the region where the semiconductor element 6 is fixed by a dispenser or the like is also known (mounting pad 3).
Not supplied to). Next, the bump electrode 7 of the semiconductor element 6
And the mounting pad 3 on the circuit board 1 are aligned with each other, and the semiconductor element 6 is pressed and pressed onto the circuit board 1 to be cured. At this time, the bump electrodes 7 of the semiconductor element 6 and the mounting pads 3 on the circuit board 1 can be electrically connected by pushing out the adhesive resin 4 existing between them.

[0006]

In the conventional flip-chip mounting method as described above, in order to increase the reliability and the yield, the bonding portion between the bump electrode of the semiconductor element and the mounting pad on the circuit board is required. The presence or absence of voids (non-filled portion of the adhesive resin) in the periphery is an important factor.

When a void is generated near the joint, the adhesive force of the adhesive resin is weakened at the joint and the joint cannot be maintained against stress such as heat, resulting in disconnection. There is.

Further, if the mounting substrate at a portion where the void is generated is exposed high temperature, a high humidity becomes a path of looking impurity ions of the circuit board by its kind for no presence of the resin, C1 ^- There is a risk that the Al pad of the semiconductor element will be corroded by the influence of the above, and the semiconductor element will be destroyed.

In particular, when a printed wiring board is used as the circuit board, an insulating solder resist is coated on portions other than the mounting pads to protect the wiring and ensure insulation. For this reason, the mounting pad of the circuit board comes to exist at the bottom of the groove of the solder resist.

The adhesive resin supply method as disclosed in Japanese Patent Laid-Open No. 4-82241 has a problem that a void is generated at the edge portion during coating.

Also in the known method of supplying the resin only to the center, when the semiconductor element is pressed and the adhesive resin is spread out, the solder resist does not flow into the groove well and exists in the groove. There is a problem that a void is generated around the joint.

[0012]

According to the flip-chip mounting method of the present invention, the first supply is performed by supplying the sealing resin a to the groove formed on the insulating film covering the circuit board and having the mounting pad on the bottom. Process, and the sealing resin a after the first supplying process.
A defoaming step of vacuum defoaming, a second supplying step of supplying a sealing resin b to the center of the mounting portion of the semiconductor element on the circuit board, and a bump of the semiconductor element A curing step of aligning the mounting pads with each other and pressing the semiconductor element against the circuit board to heat it to cure the sealing resins a and b.

The flip-chip mounting method of the present invention includes a first supplying step of supplying the sealing resin a to the groove formed in the insulating film covering the circuit board and having the mounting pad on the bottom, and the first supplying step. And a defoaming step of applying ultrasonic vibration to the sealing resin a, and a second step of supplying the sealing resin b to the center of the mounting portion of the semiconductor element on the circuit board after the defoaming step. And a curing step of aligning the bumps of the semiconductor element with the mounting pads and pressing the semiconductor element against the circuit board to heat it to cure the resin encapsulation a and b.

Further, vacuum degassing of the sealing resins a and b may be performed at the same time in the above curing step, or ultrasonic vibration may be applied to the sealing resins a and b.

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings.

[Embodiment 1] FIG. 1 is a sectional view showing a flip chip mounting method according to a first embodiment of the present invention, taken along a mounting pad portion on a circuit board.

FIG. 1A shows an unmounted circuit board 1.
The wiring of the circuit board 1 excluding the mounting pads 3 is covered with an insulating film 2 such as a solder resist, and the mounting pads 3 are formed on the bottoms of the grooves of the insulating film 2 such as a solder resist.
The material of the circuit board 1 is not particularly limited, but a printed wiring board is used in this embodiment.
Further, the thicknesses of the insulating film 2 and the mounting pad are not particularly limited, but in the present embodiment, the thickness of the solder resist 2 is 40 μm and the thickness of the pad 3 is 20 μm.
And

In this embodiment, first, as shown in FIG. 1B, the sealing resin a4 is supplied to the groove 9 of the insulating film 2. Although the screen printing method was used as the supply method in this embodiment, the supply method is not particularly limited thereto, and a known supply method such as a supply method using a dispenser may be used. The sealing resin a4 is not particularly limited as long as it has a good pouring property into the groove 9, but an epoxy resin-based thermosetting resin is used in this embodiment. The resin is completely cured at 270 ° C. in about 30 seconds.

Next, as shown in FIG.
After the step (b), the circuit board 1 is heated and left in a vacuum for defoaming. Here, the heating temperature is determined by the characteristics of the sealing resin a4 to be used, but it is the temperature before the curing is started and is the temperature at which the viscosity of the resin decreases. In this embodiment, the temperature is 60 ° C. The degree of vacuum is also determined by the characteristics of the resin, but in this embodiment, it is 5 mmHg, 15
Minutes (this was determined by evaluation,
The purpose is to completely discharge the air contained in the sealing resin a4).

Next, as shown in FIG.
Since the adhesive force is insufficient with the amount of the sealing resin a4 supplied in the step (b), the resin sealing b8 is supplied as the shortage. The supply method is the same as in the step of FIG. 4B, but in this example, the supply method using a dispenser was used. Further, the sealing resin b8 is not particularly limited as long as it has a function of adhering the semiconductor element 6 and the circuit board 1 after curing, but in the present embodiment, an epoxy resin type different from the sealing resin a4 is used. A curable resin was used. The resin is completely cured at 270 ° C. in about 30 seconds.

Finally, the bump electrodes 7 of the semiconductor element 6 and the mounting pads 3 on the circuit board 1 are aligned, and the sealing resin a
Pressurize the semiconductor element 6 while vacuum defoaming 4, b8
To heat. Here, the degree of vacuum was 5 mmHg, the amount of pressurization was 30 g per bump, the heating was 270 ° C. on the semiconductor element 6 side, the circuit substrate 1 side was 80 ° C., and the holding time was 30 sec. These conditions vary depending on the sealing resin a4 and the sealing resin b8 used.

By the above method, a mounting board of the present invention having an interface between the sealing resin a4 and the sealing resin b8 under the semiconductor element 6 as shown in FIG. 2 was obtained (the state of the interface is various). Shows two types in FIGS. 2 (a) and 2 (b) as an example).

[Embodiment 2] A flip chip mounting process according to Embodiment 2 of the present invention will be described with reference to FIG. 1 together with Embodiment 1 described above.

Also in this embodiment, the unmounted circuit board 1 is as shown in FIG.
As shown in (a), the mounting pad 3 is formed on the bottom of the groove 9 of the insulating film 2 such as a solder resist. The material of the circuit board 1 is not particularly limited, but a printed wiring board is used in this embodiment. Further, the thicknesses of the insulating film 2 and the mounting pad 3 are not particularly limited, but in this embodiment, the solder resist 2 has a thickness of 40 μm and the pad 3 has a thickness of 20 μm.

In this embodiment, first, as shown in FIG. 1B, the sealing resin a4 is supplied to the groove 9 of the insulating film 2. Although the screen printing method was used as the supply method in this embodiment, the supply method is not particularly limited, and a known supply method such as a supply method using a dispenser may be used. The sealing resin a4 is not particularly limited as long as it has a good pouring property into the groove 9, but an epoxy resin thermosetting resin is used in this embodiment. The resin is completely cured at 270 ° C. in about 30 seconds.

Next, as shown in FIG.
After the step (b), the circuit board 1 is vibrated by ultrasonic waves, and the ultrasonic vibrations are transmitted to the sealing resin a4 to remove bubbles. Here, the ultrasonic frequency is 28 kHz, and the vibration time is 1
It was set to 5 minutes (this is determined by evaluation and is intended to completely discharge the air contained in the resin in the groove 9).

Next, as shown in FIG.
Since the adhesive amount is insufficient with the amount of resin supplied in the step (b), the sealing resin b8 is supplied as the insufficient amount. The supply method is the same as the step of FIG. 1B, but in this example, the supply method using a dispenser was used. Further, the sealing resin b8 is not particularly limited as long as it has a function of adhering the semiconductor element 6 and the circuit board 1 after curing, but in the present embodiment, an epoxy resin type different from the sealing resin a4 is used. A curable resin was used. This resin is 2
The curing is completed at 70 ° C. for about 30 seconds.

Finally, the bump electrodes 7 of the semiconductor element 6 and the mounting pads 3 on the circuit board 1 are aligned, ultrasonic vibration is applied to the semiconductor element 6, and ultrasonic vibration is transmitted to the sealing resins a and b. Pressurize and heat. Here, the vibration frequency is 28
kHz, pressurization amount is 30 g per bump, heating is on the element side 2
The temperature was 70 ° C., the circuit board side was 80 ° C., and the holding time was 30 sec. These conditions vary depending on the sealing resin a4 and the sealing resin b8 used.

By the above method, a mounting board of the present invention in which an interface between the encapsulating resin a and the encapsulating resin b exists under the semiconductor element as shown in FIG. As shown in FIG. 2 (a) and (b)).

In addition, ultrasonic vibration may be applied instead of vacuum defoaming when the semiconductor element 6 of the first embodiment described above is pressed and heated to cure the sealing resin a4 and the sealing resin b8. In Example 2, vacuum degassing may be performed instead of applying ultrasonic vibration when the semiconductor element 6 is pressurized and heated to cure the sealing resin a4 and the sealing resin b8. Further, since the sealing resin a4 is degassed without performing vacuum degassing or ultrasonic vibration at these times, the bonding state between the semiconductor element and the circuit board can be improved accordingly. .

[0031]

As described above, according to the flip chip mounting method of the present invention, even if the mounting pad portion is provided in the groove of the insulating film on the circuit board, the resin can be surely supplied to the groove of the insulating film. Voids do not occur in the sealing resin around the bump pad bonding portion, and reliable bonding can be obtained.
From this, a reliable improvement is confirmed in reliability evaluations such as a temperature shock test and a pressure cooker test.

The initial yield immediately after mounting is improved.

There is an effect.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a flip-chip mounting method according to first and second embodiments of the present invention in the order of steps.

FIG. 2 is a sectional view of a semiconductor device mounted in the embodiment shown in FIG.

FIG. 3 is a cross-sectional view of a semiconductor device manufactured by a conventional flip chip mounting method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Circuit board 2 Insulating film 3 Mounting pad 4 Sealing resin a 5 Bubbles 6 Semiconductor element 7 Bump 8 Sealing resin b 9 Groove

Claims (4)

(57) [Claims] 1. A first supply step of supplying a sealing resin a to a groove formed in an insulating film covering a circuit board and having a mounting pad on the bottom thereof, and the first supply step is followed by the first supply step. Sealing resin a
A defoaming step of vacuum defoaming, a second supplying step of supplying a sealing resin b to the center of the mounting portion of the semiconductor element on the circuit board, and a bump of the semiconductor element A flip chip mounting method, which includes a curing step of aligning a mounting pad and pressing the semiconductor element against the circuit board to heat the sealing resin a and b to cure the sealing resin a and b. 2. A first supplying step of supplying a sealing resin a to a groove formed in an insulating film covering a circuit board and having a mounting pad at the bottom, and the first supplying step and the following step. Sealing resin a
Defoaming step in which ultrasonic vibration is applied to the substrate, and next to this defoaming step, the sealing resin b is provided at the center of the mounting portion of the semiconductor element on the circuit board.
And a second supplying step for supplying the semiconductor element, the bump of the semiconductor element and the mounting pad are aligned, the semiconductor element is pressed against the circuit board and heated, and the resin sealing a, b is performed.
A flip chip mounting method, comprising: 3. A resin encapsulation a, b in combination with a curing step.
3. The flip chip mounting method according to claim 1, wherein the vacuum degassing is performed. 4. A resin encapsulating resin a.
The flip chip mounting method according to claim 1, wherein ultrasonic vibration is applied to b.