JP3733264B2 - Tablet molding method and tablet molding machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a tablet molding method of a thermosetting resin molding material and a tablet molding machine used therefor, and in particular, among the thermosetting resin molding materials, a tablet molding method of an epoxy resin molding material for semiconductor encapsulation and It is related with the tablet molding machine used for it.
[0002]
[Prior art]
When a semiconductor is encapsulated with an epoxy resin molding material, etc., the epoxy resin molding material to be used is tableted, the tablet is preheated with a high frequency preheater, etc., sealed with a transfer molding machine, etc., and heat cured. Thus, a method for obtaining a semiconductor device is performed. In the case of tableting, it is tableted under normal pressure using a normal tablet molding machine. Recently, vacuum tablet molding machines are partially used in other fields, for example, tableting chemicals, but they are not used for tableting epoxy resin molding materials.
[0003]
As a vacuum tablet molding machine for chemicals, a sealed box containing a mechanism with a tableting function is connected to a powder storage hopper via one airtight valve, and a tablet canister is connected via the other airtight valve. A chemical vacuum tablet molding machine is disclosed (Japanese Patent Publication No. 7-32960), which is connected and configured so that the inside of the sealed box can be depressurized by a vacuum pump. However, the purpose of this technology is related to a vacuum tablet molding machine that can effectively eliminate adverse conditions during tablet molding such as capping and laminating, and the material is exposed to vacuum for a short time only during tableting. However, the purpose was not to influence the composition of the material.
[0004]
[Problems to be solved by the invention]
The present invention solves the problems of voids, blisters, cracks, cracks, etc. that are likely to occur when a semiconductor is encapsulated by transfer with a sealing material made of a conventional epoxy resin molding material for semiconductor encapsulation, or after molding. The purpose of this is to form tablets with extremely excellent sealing moldability by keeping the moisture content and other volatiles in the material to a minimum level without degrading physical properties and other properties. An object of the present invention is to provide a vacuum tablet molding method and a tablet molding machine used therefor.
[0005]
[Means for Solving the Problems]
The present invention introduces an epoxy resin molding material into the first vacuum hopper, reduces the content of the epoxy resin molding material and other volatile components by reducing the pressure in the first vacuum hopper, and is airtight with the first vacuum hopper. The epoxy resin molding material is transferred to a second vacuum hopper installed through a valve, the airtight valve is closed to close the first vacuum hopper and the second vacuum hopper, and the second vacuum hopper is in a vacuum state. The epoxy resin molding material is characterized in that an epoxy resin molding material is put into the tablet molding part housed in a sealed box in a vacuum state from the second vacuum hopper and continuously tableted. It is a tablet molding method. Moreover, this invention is a tablet of the epoxy resin molding material obtained by the said tablet molding method, and is a semiconductor device with which the semiconductor was sealed with this tablet.
Furthermore, the present invention is a tablet molding machine having a tablet molding part housed in a sealed box that can be in a vacuum state, and the moisture content of the epoxy resin molding material and other volatilization are formed on the top of the sealed box. The first vacuum hopper for removing the component is installed, and is intermediate between the first vacuum hopper and the sealed box, and each is connected to the first and second hermetic valves through the first hermetic valve. A second vacuum hopper for charging an epoxy resin molding material from which moisture and other volatile components have been removed in the dropped first vacuum hopper into a tablet molding portion through a second airtight valve while maintaining a vacuum state. It is a tablet molding machine characterized by being installed.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The tablet molding machine of the present invention will be described in detail with reference to FIG. FIG. 1 shows an embodiment of the present invention, and the present invention is not limited to this.
The tablet molding unit 1 is housed in a sealed box 2, and the sealed box 2 is connected to a vacuum device 11 through an airtight valve 10 so that the inside of the sealed box 2 is evacuated by the vacuum device 11. It has become. A second vacuum hopper 4 is installed on the upper part of the sealed box 2 via a second airtight valve 6, and this second vacuum hopper 4 is also connected to a vacuum device 11 via an airtight valve 9. The apparatus 11 is evacuated. A first vacuum hopper 3 is installed above the second vacuum hopper 4 via a first airtight valve 5, and this first vacuum hopper 3 is also connected to a vacuum device 11 via an airtight valve 8. The vacuum device 11 makes a vacuum state. Further, an airtight valve 7 for charging a molding material is provided on the upper portion of the first vacuum hopper 3. Of course, these have a vacuum pressure resistant structure.
[0007]
The tablet molding method of the present invention will be described in detail according to the usage pattern of the tablet molding machine of the present invention shown in FIG.
The airtight valve 8 and the first airtight valve 5 are closed, the material charging airtight valve 7 is opened, and the epoxy resin molding material is charged from the material charging airtight valve 7. After the charging is completed, the material charging hermetic valve 7 is closed, the hermetic valve 8 is opened, and the vacuum device 11 is operated to depressurize the first vacuum hopper 3 to be in a vacuum state. At this time, the degree of vacuum in the first vacuum hopper 3 is set to 80 Torr or less, preferably 30 Torr or less, so that the moisture content of the epoxy resin molding material and other volatile components are 0.05% by weight or less. Exposure to is preferred. Further, it is more preferable to provide a stirring mechanism for stirring the molding material in the first and second vacuum hoppers, and particularly when the stirring mechanism is provided in the first vacuum hopper, the time of the vacuum state can be shortened and the effect is great.
[0008]
Next, the second hermetic valve 6 of the second vacuum hopper 4 is closed, the hermetic valve 9 is opened, and the vacuum in the second vacuum hopper 4 is reduced to at least 80 Torr or less, preferably 30 Torr or less by the operation of the vacuum device 11. Then, the airtight valve 9 and the airtight valve 8 are closed, the first airtight valve 5 is opened while the material charging airtight valve 7 is closed, and the epoxy resin molding material in the first vacuum hopper 3 is dropped. Transfer into the second vacuum hopper 4. After the transfer, the first hermetic valve 5 is closed, the hermetic valve 9 is opened, and the vacuum device 11 is operated to bring the second vacuum hopper 4 into a vacuum state. Thereafter, the second airtight valve 6 is opened, and the epoxy resin molding material is dropped into the tablet molding part 1 which is in a vacuum state by opening the airtight valve 10 and the vacuum device 11 is operated. Tableting is started and a tablet is produced. While the tablet molding is being performed, a new molding material is charged again into the first vacuum hopper 3, and the tablet molding is continuously performed by repeating these operations.
[0009]
The first airtight valve 5 installed at the lower part of the first vacuum hopper 3 serving as the material supply hopper is a discharge port for the molding material of the first vacuum hopper 3, and a receiving port for the molding material of the second vacuum hopper 4. Become. The second airtight valve 6 installed at the lower part of the second vacuum hopper 4 serving as a direct material supply hopper to the tablet molding unit 1 is a discharge port for molding material of the second vacuum hopper 4. It becomes the receiving port of the molding material.
Further, it is desirable that the degree of vacuum in the tablet molding portion 1 is kept at least 80 Torr or less, preferably 30 Torr or less.
[0010]
【Example】
4.2 parts by weight of epoxy resin, 4.3 parts by weight of phenol resin, 0.2 part by weight of curing accelerator, 86.0 parts by weight of silica powder, 0.5 part by weight of silane coupling agent, 1.0 weight of antimony trioxide 1 part by weight, 1.0 part by weight of brominated epoxy resin, 0.5 part by weight of carnauba wax, 0.3 part by weight of carbon black are mixed at room temperature using a mixer, kneaded at 100 ° C. using a biaxial roll, and then cooled. The molding material was obtained by grinding. This molding material is converted into a normal tablet molding machine (hereinafter referred to as a normal molding machine), a vacuum tablet molding machine (hereinafter simply referred to as a vacuum molding machine) in which only the tablet molding part is evacuated, and a vacuum tablet molding machine of the present invention ( (Hereinafter referred to as the vacuum forming machine of the present invention) was tableted, and a package that was likely to generate voids was sealed with the tableted sample for evaluation. In addition, the material used for the vacuum forming machine of the present invention is obtained by treating the molding material in the first hopper for 1 hour at a degree of vacuum of 35 Torr. The water content of this material was 0.03% by weight, and the total content of methanol and ethanol was 3 ppm. In addition, the water content is measured by the weight change rate after 24 hours of measurement at a vacuum degree of 600 mmHg after precisely weighing about 5 g of the molding material pulverized to a maximum particle size of 2 mm or less, enclosed in a pressure-resistant airtight container containing pentoxide, The total content of methanol and ethanol was measured by gas chromatography.
Specifically, tablets each having a size of 9.8 mm and 2.9 g were formed, using each tablet-molded sample, using a low-pressure transfer molding machine, 175 ° C., 40 kg / cm ² , transfer time 4 seconds, cure time Under the condition of 90 seconds, a dummy lead frame for testing was sealed in 100 pQFP of 20 mm × 20 mm × 2.7 mm thickness with one pot and one cavity, and the surface of the molded package was observed with a microscope. The number of external voids and the maximum diameter were compared. The results are shown below. Compared with the conventional method, in the method of the present invention, the number of voids is reduced to 1/7 or less, and the generation is performed with the smallest size.
[0011]
(1) Comparison of the number of voids generated in the conventional method and the method of the present invention using a normal molding machine and the vacuum molding machine of the present invention Number of samples: 48 each Preheating time: Clamp left for 15 seconds after charging the tablet Starting void size (mils) 1 2 3 4 5 6 7 8 9 10 11 ~ 20 Total
Normal molding machine 1 2 2 1 1 7/48
Vacuum forming machine of the present invention 1 1/48
[0012]
(2) Comparison of the number of voids generated in the conventional method, the simple vacuum forming method and the method of the present invention using a normal molding machine, a simple vacuum forming machine and the vacuum forming machine of the present invention: 24 samples each Time: Clamp start void size (mils) after leaving tablet for 12 seconds 1 2 3 4 5 6 7 8 9 10 11-20 Total
Normal molding machine 1 1 1 1 4/24
Just a vacuum forming machine 1 1 2/24
Vacuum forming machine of the present invention 0/24
[0013]
【The invention's effect】
According to the present invention, the moisture and other volatile components inside the tablet of the epoxy resin molding material for semiconductor sealing can be suppressed to a very low level, so that the integrated molding high grade of semiconductor is more integrated It is very effective in preventing voids, blisters, cracks and cracks in semiconductor devices.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory view of a vacuum tablet molding machine according to one embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Tablet shaping | molding part 2 Sealed box 3 1st vacuum hopper 4 2nd vacuum hopper 5 1st airtight valve 6 2nd airtight valve 7 Material-tight airtight valve 8 Airtight valve 9 Airtight valve 10 Airtight valve 11 Vacuum apparatus

Claims (3)

  An epoxy resin molding material is put into the first vacuum hopper, the inside of the first vacuum hopper is decompressed to remove moisture and other volatile components contained in the epoxy resin molding material, and the first vacuum hopper is connected with an airtight valve. The epoxy resin molding material is transferred to the installed second vacuum hopper, the airtight valve is closed to close the first vacuum hopper and the second vacuum hopper, and while keeping the second vacuum hopper in a vacuum state, A tablet molding method for an epoxy resin molding material, wherein an epoxy resin molding material is charged from a second vacuum hopper into a tablet molding section housed in a sealed box in a vacuum state and continuously tableted.   The tablet molding method according to claim 1, wherein the inside of the first vacuum hopper is depressurized so that the water content and other volatile components contained in the epoxy resin molding material are 0.05% by weight or less.   A tablet molding machine having a tablet molding part housed in a sealed box capable of being in a vacuum state, in order to remove moisture contained in the epoxy resin molding material and other volatile components at the top of the sealed box The first vacuum hopper is installed in the middle of the first vacuum hopper and the sealed box, and each is connected by a first airtight valve and a second airtight valve, and the first vacuum hopper is dropped through the first airtight valve. A second vacuum hopper is installed to feed the epoxy resin molding material from which moisture and other volatile components have been removed in a vacuum hopper into a tablet molding part through a second airtight valve while maintaining a vacuum state. A tablet molding machine characterized by that.

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