JPH07273135A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To manufacture a semiconductor device having a good resin sealed surface efficiently in safety by effecting the cleaning on the surface of a molding die and the deburring simply and efficiently. CONSTITUTION:A semiconductor element is resin sealed by transfer molding to manufacture a semiconductor device. A cleaning sheet is sandwiched by a pair of transfer molding die and hot pressed prior to transfer molding thus cleaning the molding surface of a pair of transfer molding dies using a cleaning sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device manufacturing method.

[0002]

2. Description of the Related Art Semiconductor elements such as transistors, ICs, and LSIs are sealed in ceramic packages or plastic packages to form semiconductor devices. The ceramic package itself has heat resistance,
It has excellent moisture resistance, so it is strong against temperature and humidity.
Moreover, since it is a hollow package, high mechanical strength and highly reliable sealing are possible. However, since the constituent materials are relatively expensive and there is a drawback that mass productivity is insufficient, recently, resin sealing using a plastic package instead of the ceramic package has become mainstream.
An epoxy resin composition is used for this type of resin encapsulation, and resin encapsulation is performed by casting, compression molding, injection molding, transfer molding, or the like. And resin encapsulation by transfer molding, which excels in workability, is a prize.

[0003]

However, when the semiconductor element is resin-sealed with the epoxy resin composition by the transfer molding as described above, if the molding is continuously performed, the separation in the epoxy resin composition is prevented. The transfer agent is contaminated by the mold agent, which causes a problem that good molding cannot be achieved. That is, at the time of the above-mentioned molding, the release agent contained in the epoxy resin composition exudes to the surface of the mold to exert a release action,
When the molding is repeated, the release agent exuded on the mold surface is
The layers are sequentially laminated on the surface of the mold, and gradually deteriorated by oxidation to form a hard release agent oxidation deterioration layer (the surface is not smooth like the mold). Then, the molding material comes to be molded on the surface of the oxidation-deteriorated layer, and the surface of the oxidation-deteriorated layer is transferred to the molded product, so that the surface of the molded product is not roughened and gloss is not generated. Cause Further, once such an oxidation-deteriorated layer of the release agent is formed on the surface of the mold, the release agent exuding from the composition when molding the epoxy resin composition is It acts not on the mold surface but on the oxidation-deteriorated layer of the above-mentioned mold release agent, so that a sufficient mold release effect cannot be exhibited. In order to solve such problems,
Conventionally, as shown in the drawings, a semiconductor element having a lead frame 5 is positioned in a cavity 4 formed by an upper die 2 and a lower die 3 of a molding die 1, and the lead frame 5 is placed in the cavity 4 described above. Is positioned between the upper mold 2 and the lower mold 3 which are adjacent to each other, and in that state, a melamine resin molding material is cast and molded and cured, and the mold release agent oxidation deterioration layer on the surface of the mold is used as the molded product. It is performed that the surface of the mold is cleaned by taking out a molded product which is integrated and the oxidation deterioration layer is integrated from the mold 1. In this case, the lead frame is positioned in the cavity 4 and the melamine resin molding material is cast by the upper mold 2 adjacent to the cavity 4 with the upper mold 2 and the lower mold 3 closed. Since there is a gap 6 for the lead frame 5 in the portion between the lower molds 3, if the lead frame 5 is not positioned there and only the melamine resin molding material is poured into the cavity 4, the upper mold 2 and the lower mold 2 are This is because the melamine resin molding material escapes from the space 6 between the mold 3 and the mold 3 and molding cannot be performed sufficiently. However, when cleaning the die surface in this manner, the lead frame must be properly positioned in each cavity 4 to be cleaned, as described above, and the work is complicated and at the same time, Formalin is by-produced as a condensate of the melamine resin molding material to generate an odor and the like, which deteriorates the work environment and causes a decrease in workability of the cleaning work. Further, when the semiconductor element is resin-sealed by the transfer molding as described above,
Burrs are generated in the peripheral portion of the cavity 4, and the burrs are automatically removed by the air blown from the air nozzle, but sometimes the mold 1 that cannot be processed by the air nozzle is used. Occasionally, burrs may be generated on the part of, and in that case, a person must remove the burrs by using a finger or the like. Generally, the transfer molding is performed by automatic molding, and in the above cases, it is standardized that the automatic molding is temporarily stopped and the apparatus is stopped to deburr. There is. However, if the work is delayed, rarely while automatic molding continues, insert a finger or the like between the molds 2 and 3 within a short time when the mold 1 is open, Burrs that cannot be completely removed by the nozzle are removed, which is extremely dangerous.

The present invention has been made in view of the above circumstances, and a semiconductor device having a good sealing resin surface can be efficiently and safely manufactured by simply and efficiently cleaning the mold surface and deburring. The purpose is to provide a method that can be manufactured.

[0005]

In order to achieve the above object, the present invention is a method of manufacturing a semiconductor device in which a semiconductor element is resin-sealed by transfer molding to manufacture a semiconductor device. Prior to the step 1, the cleaning sheet is sandwiched between the pair of transfer molding dies and heated and pressed to clean the die surfaces of the pair of transfer molding dies with the cleaning sheet.

[0006]

In other words, as described above, the cleaning sheet is sandwiched between the pair of transfer molding dies and heated and pressed to position the lead frames one by one in the cavity of the molding dies as in the conventional case. The mold surface can be cleaned without requiring complicated work. At this time, formalin odor is not generated unlike the conventional case. As a result, the efficiency of mold cleaning can be increased. At that time, burrs adhering to the part of the mold surface adjacent to the cavity are also adhered to and removed from the cleaning sheet at the same time. The dangerous work of inserting and deburring is completely unnecessary, and deburring can be performed safely. In this way, it becomes possible to efficiently and safely manufacture a semiconductor device in which the surface of the sealing resin is well molded.

According to the present invention, the mold surface of the transfer mold is cleaned using the cleaning sheet. The cleaning sheet is made of, for example, unvulcanized rubber cloth made of unvulcanized rubber and a removal aid.

As the unvulcanized rubber, natural rubber (N
R), chloroprene rubber (CR), butadiene rubber (B
R), nitrile rubber (NBR), ethylene propylene terpolymer rubber (EPT), ethylene propylene rubber (EPM), styrene butadiene rubber (SBR), polyisoprene rubber (IR), butyl rubber (IIR), silicone rubber (Q), A fluororubber (FKM) or the like as a main component, a vulcanizing agent, and optionally a vulcanization accelerator and a reinforcing agent are used. This unvulcanized rubber is vulcanized into a vulcanized rubber in the mold. The above-mentioned unvulcanized rubber is preferably EPT, SBR, NBR or a mixture thereof. The EPT is a cyclic or acyclic copolymer having ethylene, α-olefin and a non-conjugated double bond. More specifically, EPT is a terpolymer composed of ethylene, α-olefin (particularly propylene) and the polyene monomers listed below, and the polyene monomers include dicyclopentadiene, 1,5-cyclooctadiene, and 1-cyclooctadiene. , 1-cyclooctadiene, 1,6-cyclododecadiene, 1,7-cyclododecadiene, 1,5,9-cyclododecatriene, 1,4-cycloheptadiene, 1,4-cyclohexadiene, norbornadiene, Methylene norbornene,
2-Methylpentadiene-1,4,1,5-hexadiene, 1,6-heptadiene, methyl-tetrahydroindene, 1,4-hexadiene and the like. The copolymerization ratio of each monomer is preferably 30 to 80 mol% of ethylene,
The ratio is such that the polyene is 0.1 to 20 mol% and the rest is α-olefin. More preferably, ethylene is 30 to 60 mol%. The Mooney viscosity ML _{1 + 4} (100 ° C.) is preferably 20 to 70. Specific examples of the EPT include Mitsui EPTs 4021, 4045, and 4070 manufactured by Mitsui Petrochemical Co., Ltd. Also, SBR has a styrene content of 15
Mooney viscosity ML _{1 + 4} (100 ° C) is 2 at ~ 30 mol%
Those of 0 to 80, preferably 35 to 60 are suitable.
Specific examples thereof include JSR-1502, JSR-1507, and JSR-1778, manufactured by Japan Synthetic Rubber Co., Ltd. The NBR has an acrylonitrile content of 20 to 60 mol%, preferably 25 to 45 mol%, and a Mooney viscosity ML _{1 + 4} (1
It is suitable to use one having a temperature of 00 ° C.) of 20 to 85, preferably 30 to 70. As a specific example, N-234L, 230S, and 230SH manufactured by Japan Synthetic Rubber Co., Ltd. can be mentioned.

The removal aids used with the unvulcanized rubber are glycol ethers, imidazoles and imidazolines, which may be used alone or in combination.

As the glycol ethers, those represented by the following general formula (1) are preferable.

[0011]

[Chemical 1]

Specific examples thereof include ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether,
Examples thereof include diethylene glycol monobutyl ether, diethylene glycol diethyl ether, diethylene glycol propyl ether, diethylene glycol dibutyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether and ethylene glycol monobutyl ether.

The glycol ether represented by the above general formula (1)
Among the ethers, n = 1 to 2, R ₁, R₂One of
When is hydrogen, the other is an alkyl group having 1 to 4 carbon atoms.
And also R₁, R₂When both are alkyl groups,
An alkyl group having 1 to 4 carbon atoms is preferable.
When n is 3 or more, the phase with rubber is
This will cause a decrease in solubility, and will also cause alkyl-based charcoal.
When the prime number is 5 or more, the release agent is added to the oxidation-deteriorated layer.
There is a tendency for poor permeability.

As the imidazoles, it is possible to obtain good results by using the imidazoles represented by the following general formula (2). Typical examples of such imidazoles include 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 1-benzyl-2-methylimidazole, and 2,4-diamino-6 [2. '-Methylimidazolyl (1)'] ethyl-s
-Triazine, 2,4-diamino-6 [2'-ethyl-
4'-methylimidazolyl- (1) '] ethyl-s-triazine and the like.

[0015]

[Chemical 2]

As the above-mentioned imidazolines, it is possible to obtain good results by using the imidazolines represented by the following general formula (3). Typical examples of such imidazolines include 2-methylimidazoline and 2-methyl-4.
-Ethylimidazoline, 2-phenylimidazoline, 1
-Benzyl-2-methylimidazoline, 2-phenyl-
4-methyl-5-hydroxymethyl imidazoline, 2,
4-diamino-6 [2'methylimidazolyl-
(1) ′] Ethyl-s-triazine, 2,4-diamino-6 [2′-methyl-4′-ethylimidazolyl-
(1) ′] Ethyl-s-triazine, 1-cyanoethyl-2-methylimidazoline, 1-cyanoethyl-2-methyl-4-ethylimidazoline and the like.

[0017]

[Chemical 3]

The above glycol ethers, imidazoles and imidazolines may be used as they are, or in a mixture with water or an alcohol such as methanol, ethanol or n-propanol, or an organic solvent such as toluene or xylene. Good. When mixed with an organic solvent, the amount of the organic solvent is usually glycol ethers,
The total amount of imidazoles and imidazolines is 100 parts by weight (hereinafter abbreviated as "part"), and is 50 parts or less, and most commonly 20 parts or less. Further, a conventionally used release agent such as stearic acid, carnauba wax, or stearylethylenediamide may be used in an appropriate amount, if necessary. When a release agent is used in combination, the amount used is unvulcanized rubber,
The total amount of 100 parts with at least one of the glycol ethers, imidazoles and imidazolines is 10 parts or less, and most commonly 2 to
There will be 5 copies.

The above glycol ethers, imidazoles and imidazolines, alone or in combination, are mixed with the above unvulcanized rubber to form unvulcanized rubber material and a cleaning sheet. In this case, the glycol ethers, imidazoles, and imidazolines alone or in combination are usually 5 to 60 parts with respect to 100 parts of the unvulcanized rubber.
Partly compounded. Preferred is 15 to 25 parts. The glycol ethers have a boiling point of 130 to 2
It is preferably about 50 ° C. That is, the mold molding is usually performed at 150 to 185 ° C., and if the boiling point of the glycol ether is less than 130 ° C., the evaporation during cleaning is remarkable, and therefore the cleaning work environment may deteriorate. On the contrary, when the temperature exceeds 250 ° C., it becomes difficult to evaporate and remains in the vulcanized rubber, and the strength of the vulcanized rubber when it is taken out from the mold is weakened and the metal is deformed. This is because it becomes difficult to sufficiently peel off the oxidation-deteriorated layer of the release agent from the mold surface, and the workability for cleaning tends to decrease.

Further, the cleaning sheet made of the unvulcanized rubber material may be blended with an inorganic reinforcing agent (filler) such as silica, alumina, calcium carbonate, aluminum hydroxide, titanium oxide as a reinforcing agent. is there. In this case, the amount of the reinforcing agent used is preferably set to 10 to 50 parts per 100 parts of unvulcanized rubber.

The cleaning sheet made of unvulcanized rubber material preferably has a total content of chlorine ions and sodium ions of 2000 ppm or less. That is, when cleaning the die surface of the transfer mold with the above cleaning sheet, chlorine ions and sodium ions contained in the cleaning sheet remain on the die surface, and these ionic impurities are contained in the semiconductor device. This is because there is a risk that they will enter, and if the above-mentioned ionic impurities enter these semiconductor devices, a serious problem will occur in terms of reliability such as moisture resistance reliability. Therefore, when manufacturing the cleaning sheet made of the unvulcanized rubber fabric, it is desirable to thoroughly examine the raw materials used and to use the one that does not contain the above ionic impurities.

Although the above description has been made with respect to the cleaning sheet made of the unvulcanized rubber cloth, the cleaning sheet is not limited to this, and has the effect of removing the release agent oxidative deterioration layer and the like. Anything can be used as long as it is.

According to the present invention, when the semiconductor element is continuously resin-sealed by transfer molding to continuously manufacture the semiconductor device, the mold surface of the molding die is washed with the above cleaning sheet. After that, transfer molding is further appropriately performed to manufacture a semiconductor device. On this occasion,
The molding material used for sealing is not particularly limited, and a conventionally known molding material such as an epoxy resin molding material is used, and molding conditions and the like are set according to the conventional method.

The semiconductor device manufactured in this manner is
Since the molding die is molded in a good cleaning state, the surface condition of the sealing resin is extremely good.

[0025]

According to the present invention, prior to transfer molding, a cleaning sheet is used to remove the oxidation-deteriorated layer of the release agent formed on the surface of the mold, and deburring is performed. Therefore, cleaning of the mold is extremely easy. It can be carried out without causing odor or the like. Also, deburring can be performed safely. As a result, a semiconductor device in which the surface state of the sealing resin is extremely good can be manufactured with high efficiency, continuously, and safely.

Next, examples will be described in detail together with comparative examples.

[0027]

Example 1 Ethylene propylene terpolymer rubber (E
PT, Mitsui Petrochemical Industry Co., Ltd., Mitsui EPT4045) 1
After kneading 00 parts, 20 parts of silica powder, 5 parts of titanium oxide, 4 parts of organic peroxide, 1 part of stearic acid and 20 parts of diethylene glycol dibutyl ether with a kneading roll, a rolling roll is used to form a sheet having a thickness of 7 mm. A mold cleaning composition was obtained.

[0028]

Example 2 In place of diethylene glycol dibutyl ether, ethylene glycol monoethyl ether was used. A sheet-like mold cleaning composition was obtained in the same manner as in Example 1 except for the above.

[0029]

Example 3 100 parts of styrene butadiene rubber (SBR, JSR-1502 manufactured by Japan Synthetic Rubber Co., Ltd.), 20 parts of silica powder, 15 parts of aluminum hydroxide, 4 parts of organic peroxide, 1 part of zinc stearate, 1 part of diethylene glycol monomethyl. A sheet-shaped mold cleaning composition was obtained in the same manner as in Example 1 using 15 parts of ether.

[0030]

Example 4 100 parts of nitrile rubber (NBR, N-230SH manufactured by Japan Synthetic Rubber Co., Ltd.), silica powder 20
Part, titanium oxide 5 parts, organic peroxide 4 parts, stearic acid 1 part, and ethylene glycol monoethyl ether 15 parts to obtain a sheet-shaped mold cleaning composition in the same manner as in Example 1.

[0031]

Example 5 The usage rate of ethylene glycol monoethyl ether was reduced to 12 parts. Otherwise in the same manner as in Example 4, a sheet-like mold cleaning composition was obtained.

[0032]

Example 6 The amount of ethylene glycol monoethyl ether used was increased to 55 parts. Otherwise in the same manner as in Example 4, a sheet-like mold cleaning composition was obtained.

[0033]

Example 7 EPT was not used alone, but was used in combination with the SBR used in Example 3 (50:50). A sheet-like mold cleaning composition was obtained in the same manner as in Example 1 except for the above.

[0034]

Example 8 Ethylene propylene terpolymer rubber (E
PT, Mitsui Petrochemical Industry Co., Ltd., Mitsui EPT4045) 1
After kneading 00 parts, silica powder 20 parts, titanium oxide 5 parts, organic peroxide 4 parts, stearic acid 1 part, and 2-ethyl-4-methylimidazole 3 parts with a kneading roll, a rolling roll is used to obtain a thickness of 7 mm. The sheet was formed into a sheet to obtain the intended mold cleaning composition.

[0035]

Examples 9, 10 The amount of 2-ethyl-4-methylimidazole was changed to 20 parts and 50 parts, respectively. Other than that was carried out similarly to Example 1, and obtained the target mold-cleaning composition.

[0036]

Examples 11, 12 Instead of 2-ethyl-4-methylimidazole, 2,4-diamino-6 [2'-methylimidazolyl- (1) '] ethyl-s-triazine (hereinafter "2MZ-AZINE") was used. Abbreviated) was used in 3 parts and 20 parts, respectively. A sheet-like mold cleaning composition was obtained in the same manner as in Example 1 except for the above.

[0037]

Example 13 In place of 2-ethyl-4-methylimidazole, 10 parts of 2MZ-AZINE and 10 parts of 1-cyanoethyl-2-methylimidazole were used in combination. A sheet-like mold cleaning composition was obtained in the same manner as in Example 1 except for the above.

[0038]

Examples 14 and 15 100 parts of styrene-butadiene rubber (SBR, JSR-1502 manufactured by Japan Synthetic Rubber Co., Ltd.) was used instead of the ethylene propylene terpolymer rubber, and
5 parts and 20 parts of 2-methylimidazoline were used instead of ethyl-4-methylimidazole, respectively. A sheet-like mold cleaning composition was obtained in the same manner as in Example 1 except for the above.

[0039]

[Examples 16 and 17] Half of the ethylene propylene terpolymer rubber was replaced with the styrene-butadiene rubber, and 2-phenyl-4-methylimidazole was replaced with 2-phenylimidazoline in an amount of 5 parts and 20 parts, respectively.
A sheet-like mold cleaning composition was obtained in the same manner as in Example 1 except for the above.

[0040]

Example 18 In place of the ethylene propylene terpolymer, 50 parts of the above styrene-butadiene rubber and 50 parts of nitrile rubber (NBR, N-230SH manufactured by Nippon Synthetic Rubber Co., Ltd.) were used and 2-ethyl-4-methylimidazole was prepared. Instead 1-cyanoethyl-2-methylimidazole 10
Parts and 10 parts of 1-cyanoethyl-2-methyl-4-ethylimidazoline. A sheet-like mold cleaning composition was obtained in the same manner as in Example 1 except for the above.

[0041]

Comparative Example 1 2-Amino-2-methyl-1-propanol was used in place of diethylene glycol dibutyl ether. A sheet-like mold cleaning composition was obtained in the same manner as in Example 1 except for the above.

[0042]

Comparative Example 2 Toluene was used instead of ethylene glycol monoethyl ether. A sheet-like mold cleaning composition was obtained in the same manner as in Example 2 except for the above.

[0043]

Comparative Example 3 Diisopropyl ketone was used in place of diethylene glycol monomethyl ether. Otherwise in the same manner as in Example 3, a sheet-shaped mold cleaning composition was obtained.

[0044]

Comparative Example 4 Ethanol was used in place of ethylene glycol monoethyl ether. Otherwise in the same manner as in Example 4, a sheet-like mold cleaning composition was obtained.

The mold cleaning composition obtained in each of the above Examples and Comparative Examples was sandwiched between thermosetting resin molding molds in which an oxidation-deteriorated layer of a release agent was formed, and heated at 175 ° C. for 4 minutes. Sulphate,
Immediately after vulcanization, the mold was opened and the molded vulcanized rubber was taken out. In this case, the mold surface cleanability and the deterioration of the work environment due to the odor were investigated. In addition, using a mold after cleaning, a semiconductor element is transfer-molded under normal conditions into a semiconductor device, and the surface state of the sealing resin of the obtained device is visually observed, and the result is the above test results. In addition, the results are collectively shown in Tables 1 to 5 below.

[0046]

[Table 1]

[0047]

[Table 2]

[0048]

[Table 3]

[0049]

[Table 4]

[0050]

[Table 5]

As is clear from Tables 1 to 5 above, according to the examples, the surface of the vulcanized rubber taken out from the thermosetting resin molding die has a release agent oxidation deterioration layer on the surface of the die. Transferred and adhered, whereby the cavity surface of the mold was sufficiently cleaned. In addition, no odor was generated during the cleaning work, and therefore the cleaning workability was not a problem at all. On the other hand, in the comparative example, there were problems in mold cleaning property or odor, and good results were not obtained. As a result, regarding the sealing resin of the semiconductor device obtained by using the above-mentioned mold, the surface of the resin had smoothness and gloss, while the comparative example, especially the comparative example 2
Nos. 4 to 4 were slightly uneven and were not glossy.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a conventional example.

Front Page Continuation (72) Koichi Takashima, 2307, Yoshida, Ota, Mitagawa-cho, Kanzaki-gun, Saga Prefecture 2 Kyushu Nitto Denko Corporation

Claims (5)

[Claims] 1. A method of manufacturing a semiconductor device in which a semiconductor element is resin-sealed by transfer molding to manufacture a semiconductor device, wherein a cleaning sheet is provided between a pair of transfer molding dies prior to the transfer molding. A method of manufacturing a semiconductor device, comprising cleaning the mold surfaces of the pair of transfer molding dies with the cleaning sheet by sandwiching, heating and pressing. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the cleaning sheet is made of unvulcanized rubber material. 3. The method of manufacturing a semiconductor device according to claim 2, wherein the unvulcanized rubber material comprises unvulcanized rubber and a removal aid. 4. The method for manufacturing a semiconductor device according to claim 3, wherein the removal aid is at least one compound selected from the group consisting of glycol ethers, imidazoles, and imidazolines. 5. The method for producing a semiconductor device according to claim 2, wherein the unvulcanized rubber material has a total content of chlorine ions and sodium ions suppressed to 2000 ppm or less.