JP3351996B2 - Semiconductor device manufacturing method and semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device obtained by encapsulating a semiconductor element on a wiring board, and to a semiconductor device.

[0002]

2. Description of the Related Art In manufacturing a semiconductor device by mounting a semiconductor element on a wiring board, the semiconductor element is mounted on the wiring board, and the semiconductor element is electrically connected to the wiring board by bonding wires, After electrically connecting a semiconductor element to a wiring board with bumps provided in the semiconductor device, the semiconductor element is sealed with a sealing material.

Conventionally, the sealing material is generally sealed with a dispenser.
That is, a liquid sealing material is applied to a semiconductor element mounted on a wiring substrate by a dispenser to perform sealing. However, when applying a sealing material with a dispenser to perform sealing, it is necessary to use a sealing material having high thixotropy so that the applied sealing material does not flow, which increases the cost of the material. Met.

Therefore, the present applicant has been studying to seal the sealing material 4 by a printing method. FIG. 5 (a)
Shows an example of such a case, in which an opening 6 is provided to form a mask 5, the mask 5 is overlaid on the wiring substrate 3 so as to surround the semiconductor element 1 in the opening 6, and the mask 5 is supplied on the mask 5. After printing the sealing material 4 through the opening 6 of the mask 5 by rubbing the liquid sealing material 4 with a squeegee 7,
By removing the mask 5 and curing the sealing material 4, the semiconductor element 1 can be sealed with the sealing material 4 as shown in FIG.

However, even in this case, when printing is performed under atmospheric pressure, air is entrained in the liquid sealing material 4,
There is a problem that bubbles remain in the sealing portion and void defects occur. In this case, voids can be removed by defoaming under reduced pressure after printing, but a bubble escape mark remains on the surface, and there is a problem that the sealing portion cannot be formed to have a smooth surface. For this, 3 Torr
Printing under the following reduced-pressure atmosphere has been studied. By performing printing in a reduced-pressure atmosphere of 3 Torr or less in this manner, air is prevented from being caught in the sealing material 4 and generation of bubbles in the sealing material 4 can be prevented. After returning the atmosphere to the atmospheric pressure, the semiconductor element 1 can be sealed by removing the mask 5 and curing the sealing material 4.

[0006]

However, when printing is performed in a reduced pressure atmosphere of 3 Torr or less as described above, the surface of the printed encapsulating material 4 is printed during the process of returning the atmosphere to atmospheric pressure after printing. What was smooth is shown in FIG.
As shown in (c), the central portion is deformed so as to be dented and the contour portion is raised, so that the upper surface of the sealing material 4 has an uneven surface with a height difference of about 50 to 60 μm. When the upper surface of the sealing material 4 has such an uneven surface, the sealing performance becomes unstable.

[0007] The present invention has been made in view of the above points, and it is possible to seal by reducing the generation of bubbles and to seal the upper surface of the sealing material by finishing it to a smooth surface. It is an object of the present invention to provide a method for manufacturing a semiconductor device and a semiconductor device.

[0008]

According to a method of manufacturing a semiconductor device according to the present invention, a semiconductor element 1 is electrically connected to a wiring substrate 3 and mounted thereon, and a mask 5 formed with an opening 6 is formed in the opening. 6, the semiconductor element 1 is positioned on the wiring substrate 3 with the sealing material 4 supplied on the mask 5 being 3 Torr.
The sealing material 4 is sealed and printed through the opening 6 of the mask 5 by rubbing with a squeegee 7 under a reduced pressure condition of r or less, and the sealing material 4 on the mask 5 is further squeezed under atmospheric pressure conditions. The semiconductor element 1 is sealed with the sealing material 4 by finishing printing the sealing material 4 through the opening 6 of the mask 5 by rubbing with 7.

Further, the semiconductor device of the present invention is characterized in that the semiconductor element 1 is sealed on the wiring board 3 by the above method.

[0010]

Embodiments of the present invention will be described below. The wiring board 3 is formed by a printed wiring board or the like. First, a semiconductor element (semiconductor chip) 1 is mounted on the wiring board 3 and is electrically connected. Wiring board 3
The semiconductor element 1 is electrically connected to the semiconductor element 1 by connecting a bonding wire 8 between an electrode on the upper surface of the semiconductor element 1 and an electrode on the wiring board 3 or by bumping the lower surface of the semiconductor element 1 with solder or the like. 2, the semiconductor element 1 is mounted on the wiring board 3 and the bumps 2 are bonded to the electrodes of the wiring board 3.

FIG. 1 shows an apparatus for sealing a semiconductor element 1 mounted on a wiring board 3 with a sealing material 4 as described above. A substrate receiving tray 13 is placed on the work table 12. The substrate receiving tray 13 is formed by providing a frame piece 14 having substantially the same height as the thickness of the wiring board 3 on the peripheral upper surface. Is mounted, and a mask 5 is placed and set from the upper surface of the wiring substrate 3 to the upper surface of the frame piece 14. The mask 5 is formed by stretching a metal plate or the like below the frame 15, and an opening 6 is formed in the mask 5 at a location where the semiconductor element 1 is sealed. The mask 5 is set on the wiring board 3 so that the semiconductor element 1 is located inside the opening 6.

The work table 12 is divided into a setting zone 16 and a printing zone 17 for setting the wiring board 3 on the board receiving tray 13 and setting the mask 5 on the wiring board 3. After performing in the setting zone 16, the liquid sealing material 4 such as an epoxy resin is supplied onto the mask 5 in the setting zone 16. The supply of the sealing material 4 can be performed using a syringe 18 or the like. Here, as the sealing material 4, one having a filling amount of the inorganic filler of 40 to 85% by weight, a viscosity of 100 to 5000 ps (25 ° C.), and a thixotropic index of 1.0 to 4.5 (25 ° C.) is used. Is preferred.

Thus, the setting of the mask 5 and the sealing material 4
Then, the substrate receiving tray 13 is moved to the printing zone 17. The printing zone 17 is provided with a vacuum chamber 21. The vacuum chamber 21 is formed in a box shape whose lower surface is open, and the base is a bearing 22.
It is attached to the tip of a rotating bar 23 pivotally supported by the. Accordingly, the vacuum chamber 21 is rotated upward of the work table 12 to open the lower opening, and is rotated downward to close the opening edge of the lower surface closely to the upper surface of the work table 12. It is designed to be turned up and down between the states. A squeegee driving device 24 formed by an air cylinder or the like is provided on an outer surface of the vacuum chamber 21. A squeegee slide bar 25 protruding inward of the vacuum chamber 21 is provided on the squeegee driving device 24.
Is provided. The squeegee slide bar 25 is formed so as to reciprocate in the vacuum chamber 21 in accordance with the operation of a plunger in a cylinder of the squeegee driving device 24, and the squeegee 7 is attached to the tip thereof. The squeegee 7 is formed of a synthetic resin plate or the like. The worktable 12 is provided with a vacuum pipe 26 connected to a decompression device such as a vacuum pump, and the vacuum pipe 26 is opened on the upper surface of the worktable 12. The opening of the vacuum pipe 26 is arranged so as to be located in the vacuum chamber 21 when the opening edge of the lower surface is brought into close contact with the upper surface of the worktable 12 by rotating the vacuum chamber 21 downward.

Thus, the substrate receiving tray 13 is moved from the setting zone 16 to the printing zone 17 while the vacuum chamber 21 is rotated above the work table 12 as indicated by a chain line. After moving to the printing zone 17, the vacuum chamber 2
1 is rotated downward, and the substrate receiving tray 13 is surrounded by the vacuum chamber 21. When the vacuum chamber 21 is rotated downward as described above, the squeegee 7 comes into contact with the upper surface of the mask 5. Next, vacuum piping 26
The air in the vacuum chamber 21 is discharged through
The pressure inside the vacuum chamber 21 is reduced. Thereafter, the squeegee 7 is moved along the upper surface of the mask 5 as shown by the arrow in FIG. 1, and the sealing material 4 supplied on the mask 5 is rubbed with the squeegee 7 to seal through the opening 6 of the mask 5. The stop material 4 is applied by printing, and sealing printing is performed. At this time, the squeegee 7 may be driven to reciprocate several times, and printing may be repeated a plurality of times.

The sealing material 4 is a mask 5 surrounding the semiconductor element 1.
Is filled into the opening 6 of the semiconductor device 1, and the side surface and the upper surface of the semiconductor element 1 can be covered with the sealing material 4. Since printing using the mask 5 and the squeegee 7 is performed in a reduced-pressure atmosphere, air is generated when the sealing material 4 is rubbed with the squeegee 7 to perform printing.
This eliminates the possibility that air bubbles (voids) are generated in the sealing material 4. The reduced-pressure atmosphere in the vacuum chamber 21 is set to a degree of vacuum of 3 Torr or less.
In order to perform printing so that air bubbles are not generated in the sealing material 4, it is necessary to set the degree of vacuum to 3 Torr or less. Needless to say, the lower the degree of vacuum, the better.
About 0.5 Torr is a practical lower limit.

After the sealing printing is performed in an atmosphere having a vacuum degree of 3 Torr or less as described above, when the atmosphere is returned to the atmospheric pressure, as described above, the sealing printed as shown in FIG. The surface of the material 4 becomes an uneven surface. Therefore, in the present invention, the pressure in the vacuum chamber 21 is adjusted to moderate the reduced pressure state, and after returning to the atmospheric pressure , the squeegee 7 is driven again to remove the sealing material 4 supplied on the mask 5 into the opening. Through 6, printing is applied to the upper surface of the sealing material 4 which has been printed so as to cover the semiconductor element 1, and finish printing is performed. Even if the surface of the sealing material 4 has an uneven surface by relaxing the decompression state in the vacuum chamber 21,
By performing the finish printing in this manner, the upper surface of the sealing material 4 is finished to a smooth surface as shown in FIG. In order to finish the upper surface of the sealing material 4 to a smooth surface,
As described above, the atmosphere needs to be 5 Torr or more.

After printing the sealing material 4 as described above, the inside of the vacuum chamber 21 is returned to the atmospheric pressure, and the vacuum chamber 21 is rotated upward to open the substrate receiving tray 13. Then, after returning the substrate receiving tray 13 from the printing zone 17 to the setting zone 16, the mask 5 is removed from above the wiring board 3 and the wiring board 3 is removed.
Is taken out of the substrate receiving tray 13 and the wiring substrate 3 is sent out to a step of curing the sealing material 4, whereby a semiconductor device having the semiconductor element 1 mounted and sealed on the wiring substrate 3 can be finished. FIGS. 3A, 3B, and 3C show an embodiment of the semiconductor device manufactured as described above. FIG. 3A shows that the semiconductor element 1 is connected to the wiring board 3 by bonding wires 8. FIG. 3 (b) shows the semiconductor device 1 mounted in the recess 29 of the wiring board 3 and the semiconductor element 1 mounted thereon.
FIG. 1C shows a semiconductor device 1 flip-chip mounted on a wiring board 3 with bumps 2.

When the sealing material 4 is printed and sealed as described above, a frame-shaped dam 30 is provided on the upper surface of the wiring board 3 so as to surround the semiconductor element 1 mounted on the wiring board 3. As shown in FIG. 3D, the semiconductor element 1 can be sealed with the sealing material 4 in the dam 30. In this case, the opening 6 of the mask 5 is formed in accordance with the outer shape and dimensions of the dam 30, and the mask 5 is overlaid on the upper surface of the wiring board 3 so as to surround the dam 30 with the opening 6.
In this state, by rubbing the sealing material 4 on the mask 5 with the squeegee 7 as described above, the sealing material 4 can flow into the dam 30 from the opening 6 to seal the semiconductor element 1. Things. When the dam 30 is provided in this manner, the sealing material 4 can be prevented from flowing out, so that the sealing material 4 having a small thixotropy index can be used without any problem.

Next, the present invention will be described with reference to examples. (Example 1) “Panasealer C” manufactured by Matsushita Electric Works, Ltd. as a sealing material 4
V5420 series "and a thixotropic agent (hydrophobic silicon dioxide:" RY20 "manufactured by Nippon Aerosil Co., Ltd.)
0 "), the viscosity was set to 700 ps (measured at 25 ° C. by a B-type viscometer, the same applies hereinafter) and the thixotropy index was set to 1.2 (measured at 25 ° C. by a B-type viscometer, the same applies hereinafter). . Then, the thickness of the mask 5 is 0.4 m.
Sealing printing and finish printing were performed using the apparatus shown in FIG. 1 using a stainless steel plate having an opening 6 having the same dimensions as the sealing area formed on a stainless steel plate having a thickness of m. At this time, sealing printing is vacuum
Finished printing is 760To under a reduced pressure atmosphere of 3 Torr
The test was performed in an atmosphere of atmospheric pressure of rr . Then, after printing the sealing material 4 in this manner, at 150 ° C. for one hour,
The sealing material 4 was cured at a temperature of 3 ° C. for 3 hours to obtain a semiconductor device.

In this semiconductor device, the cured sealing material 4 has a smooth upper surface as shown in FIG. 4A, and when measured by an ultrasonic flaw detector, generation of voids is also observed. Did not .

[0021]

[0022]

[0023]

Comparative Example 1 A semiconductor device was obtained in the same manner as in Example 1 except that sealing printing was performed in a reduced-pressure atmosphere at a vacuum of 3 Torr and finish printing was not performed. At this time, the semiconductor
A device provided with a dam 30 so as to surround the element 1 was used. In this semiconductor device, the sealing material 4 after curing is the same as that of FIG.
As shown in (b) , the central portion of the upper surface was a concave-convex surface with a concave portion, and no void was observed.

Comparative Example 2 A semiconductor device was obtained in the same manner as in Example 1, except that sealing printing was performed in a reduced-pressure atmosphere at a vacuum of 3 Torr, and finishing printing was also performed in a reduced-pressure atmosphere at 3 Torr. this
At this time, the upper surface of the wiring board 3 is
The one provided with the memory 30 was used. In this semiconductor device, the sealing material 4 after curing the middle portion of the upper surface as shown in FIG. 4 (c) has become uneven surface became concave and voids were observed.

(Comparative Example 3) "Panasealer C" manufactured by Matsushita Electric Works, Ltd. was used as the sealing material 4.
V5420 series "and the mixing amount of the thixotropic agent was adjusted to obtain a viscosity of 2500 ps and a thixotropic index of 4.
Set to 5. Then, a semiconductor device was obtained in the same manner as in Example 1 (without using the dam 30) except that sealing printing was performed in an atmospheric pressure atmosphere and finish printing was not performed. In this semiconductor device, although the sealing material 4 after curing has an upper surface formed as a smooth surface as shown in FIG. 4 (d) , voids 31 were found when measured by an ultrasonic flaw detector. .

[0027]

[Table 1]

[0028]

As described above, according to the present invention, a semiconductor element is electrically connected and mounted on a wiring board, and a mask formed with an opening is formed by positioning the semiconductor element inside the opening. And the sealing material supplied on the mask is 3T
The sealing material is sealed and printed through the opening of the mask by rubbing with a squeegee under a reduced pressure condition of orr, and the sealing material on the mask is further rubbed with the squeegee under the condition of atmospheric pressure and sealed through the opening of the mask. Since the semiconductor element was sealed with the sealing material by finishing printing the material,
Air upon sealing printing performed under a reduced pressure condition of at most 3Torr it prevents, as caught in the sealing material, which can be performed sealing by reducing the occurrence of bubbles, moreover atmospheric pressure By performing finish printing under the conditions described above, the upper surface of the sealing material can be finished to a smooth surface and sealed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of an embodiment of the present invention.

FIG. 2 (a) is a cross-sectional view of a printed wiring board printed with sealing;
(B) is a cross-sectional view of the printed circuit board after the finish printing.

FIGS. 3A to 3D are cross-sectional views illustrating each embodiment of the semiconductor device.

FIGS. 4A to 4D are cross-sectional views showing the states of the sealing materials of Example 1 and Comparative Examples 1 to 3. FIG.

FIG. 5 shows a conventional example, and (a) to (c) are cross-sectional views.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor element 3 Wiring board 4 Sealing material 5 Mask 6 Opening 7 Squeegee

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yasutaka Miyata 1048 Kadoma Kadoma, Osaka Pref.Matsushita Electric Works, Ltd. Inventor Hirohisa Hino 1048, Kazuma Kadoma, Kadoma City, Osaka Pref. Matsushita Electric Works, Ltd. (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/56 H01L 23/28 F-term system (JPO) WPI / L (DIALOG)

Claims (2)

(57) [Claims] 1. A semiconductor device is electrically connected to and mounted on a wiring board, and a mask formed with an opening is placed on the wiring substrate with the semiconductor element positioned inside the opening and supplied on the mask. a sealing material sealing the print through the openings in the mask rubbing squeegee sealing material which is under a reduced pressure condition of at most 3 Torr, the mask rubbed further sealing material on the mask with the squeegee under the conditions of atmospheric pressure A semiconductor element is sealed with the sealing material by finish-printing the sealing material through the opening of the semiconductor device. 2. A semiconductor device, wherein a semiconductor element is sealed on a wiring board by the method according to claim 1.