JP4634083B2 - Manufacturing method of tablets for semiconductor encapsulation - Google Patents

Description

The present invention is used in the sealing material for a semiconductor device, it relates to a manufacturing method of the semiconductor molding tablet which can suppress the generation of internal voids of the sealing resin portion.

  Conventionally, as a sealing material for semiconductor elements such as IC, LSI, etc., a powdered material is used which is prepared by blending an epoxy resin, a phenol resin and an inorganic filler, melt kneading, rolling, cooling and pulverizing. Yes. In some cases, the powdery material thus obtained is directly supplied to a molding machine for package sealing to perform resin sealing of the semiconductor device. In general, a tablet is produced by press-compressing in a metal mold, and this is supplied to a molding machine for package sealing to perform resin sealing of the semiconductor device.

  As described above, the tablet formed by compression molding in advance is used as the sealing material because the gap between the pulverized particles in the sealing material is compressed and reduced in the compression molding tablet. This is because the amount of air contained in is reduced. Therefore, by using such a tablet as a sealing material, it is difficult for voids to remain in the package and on the surface after sealing, and the reliability after sealing and the yield in the sealing process are significantly improved. Become.

However, recently, the semiconductor device has been made thinner, and in such a thin package, naturally, the thickness of the sealing resin layer is also reduced, and even if it is a void that has not been a problem in the past, The thin package causes a serious defect, so that it is required to increase the density of the tablet for the purpose of reducing the incidence of voids. For example, it has been proposed to obtain a high-density tablet by adjusting the particle filling structure by limiting the particle size distribution of the pulverized product before tableting, for increasing the density of the tablet (see Patent Document 1). . Alternatively, a method for producing an epoxy resin molding material has been proposed in which the temperature of the discharged material discharged from the kneader is specified and the properties of the molding material obtained by cooling and pulverizing the discharged material are limited (see Patent Document 2). ).
JP-A-8-39549 JP 2002-220475 A

  However, these effects can hardly be obtained in the high-density region of recent tablets, and in the end, the actual situation is that it has been dependent on the increased pressure during tableting. As a result, the tablet density ratio has already reached a level of 94% in terms of the true specific gravity ratio, and higher pressures than this will cause distortion and breakage of the molding equipment, and decrease the yield during tablet production. There is a problem, and there is currently a limit to seeking solutions for the tablet manufacturing device itself.

The present invention was made in view of such circumstances, to provide manufacturing method of the semiconductor molding tablet which can reduce generation of voids inside the package by the high density of the tablet and its purpose .

In order to achieve the above object, the present invention comprises a step of preparing a kneaded product of an epoxy resin composition containing the following components (A) to (C) as essential components, and the kneaded product having a thickness of 0.2. A step of rolling and forming into a sheet having a sheet density ratio of 98% or more at 1.0 mm, and crushing the sheet-like molded body, and then pulverizing the pulverized product with a tablet density ratio of 94% to 98% within a pressure range of 245 to 784 MPa. The manufacturing method of the tablet for semiconductor sealing provided with the process of tablet-molding in the tablet form below is made into a summary.
(A) Epoxy resin.
(B) Phenolic resin.
(C) Inorganic filler.

That is, the present inventors repeated a series of studies in order to obtain a high-density tablet that was the limit in the conventional tableting device. And only by the applied pressure when tableting the pulverized product that is a resin composition for semiconductor encapsulation as in the past, the crushed particles that have been cooled and hardened are crushed to remove the air in the powder, and more It was found that it is impossible to tablet into a high-density tablet. As a result of further research based on this knowledge, first, in the sealing material before tableting into a tablet, when the kneaded discharge material in the molten state of the compounding component of the sealing material is rolled into a sheet When the sheet is rolled and formed into a sheet with a high density ratio, and the rolled sheet is pulverized and compressed into a tablet in a pressure range of 245 to 784 MPa , the air in the powder, which is a pulverized product, is significantly removed, and the tablet is compressed. For semiconductor encapsulating, it is possible to obtain a higher-density tablet while reducing the applied pressure, and to suppress the formation of voids in the package when the semiconductor element is encapsulated using this tablet The inventors have found that a tablet can be obtained and have reached the present invention.

Thus, in the present invention, the kneaded product of the epoxy resin composition is rolled and formed into a sheet having a sheet density ratio of 98% or more, and the sheet-like formed body is pulverized, and then this pulverization is performed at a pressure in the range of 245 to 784 MPa. Tablets for semiconductor encapsulation are manufactured by tableting the product into tablets having a tablet density ratio of 94% or more and less than 98%. Thus, by setting the sheet density ratio as described above, when the pulverized product is used, it is possible to obtain a high-density tablet that is difficult to realize with the conventional tableting technology and tableting device. It becomes possible. Therefore, a semiconductor device manufactured by resin-sealing using a tablet obtained by the manufacturing method of the present invention is reduced in the generation of voids and can be highly reliable.

And since the thickness of the said roll-formed sheet | seat is set to 0.2-1.0 mm, it becomes easy to make a sheet density ratio 98% or more of high density ratios.

  In addition, when the particle size distribution of the pulverized product is 50% by weight or less of particles having a particle size of more than 1.0 mm and 10 to 40% by weight of particles having a particle size of 0.125 mm or less, tablet molding becomes easy. In a semiconductor device formed by a tablet using this pulverized product, generation of voids is further reduced.

  The tablet for semiconductor encapsulation obtained by the present invention uses an epoxy resin composition containing an epoxy resin (component A), a phenol resin (component B), and an inorganic filler (component C) as essential components. It can be obtained by kneading and forming into a sheet having a specific thickness and then pulverizing and tableting this pulverized product into a tablet.

  The epoxy resin (component A) is not particularly limited, and various conventionally known epoxy resins are used. Examples thereof include various epoxy resins such as cresol novolac type, phenol novolac type, bisphenol A type, biphenyl type, triphenylmethane type, and naphthalene type. These can be used alone or in combination of two or more.

  The phenolic resin (component B) used together with the epoxy resin (component A) serves as a curing agent for the epoxy resin, and is not particularly limited. For example, phenol novolac, cresol Examples thereof include novolak, bisphenol A type novolak, naphthol novolak, and phenol aralkyl resin. These may be used alone or in combination of two or more.

  The blending ratio of the epoxy resin (component A) and the phenol resin (component B) is blended so that the hydroxyl group equivalent in the curing agent is 0.5 to 2.0 equivalents per equivalent of epoxy group in the epoxy resin. It is preferable. More preferably, it is 0.8-1.2 equivalent.

  The inorganic filler (C component) used together with the epoxy resin (component A) and the phenol resin (component B) is not particularly limited and includes various conventionally known fillers such as quartz glass powder and talc. And silica powder (such as fused silica powder and crystalline silica powder), alumina powder, aluminum nitride powder, and silicon nitride powder. These may be used alone or in combination of two or more. Among these, it is preferable to use the silica powder from the viewpoint that the linear expansion coefficient of the obtained cured product can be reduced, and it is particularly preferable from the viewpoint of high filling and high fluidity to use the fused silica powder among the silica powders. . Examples of the fused silica powder include spherical fused silica powder and crushed fused silica powder. From the viewpoint of fluidity, spherical fused silica powder is preferably used. Among them, it is preferable to use those having an average particle diameter in the range of 10 to 60 μm, particularly preferably in the range of 15 to 45 μm. In addition, the said average particle diameter can be measured using a laser diffraction scattering type particle size distribution measuring apparatus, for example.

  The content of the inorganic filler (component C) is preferably set in the range of 50 to 95% by weight, particularly preferably 70 to 90% by weight, based on the entire epoxy resin composition.

  In the present invention, in addition to the above components A to C, a curing accelerator, a halogenated flame retardant such as brominated epoxy resin, a flame retardant aid such as antimony trioxide, a pigment such as carbon black, β- Other additives such as silane coupling agents such as (3,4-epoxycyclohexyl) ethyltrimethoxysilane and γ-glycidoxypropyltrimethoxysilane, and mold release agents such as carnauba wax are appropriately used.

  The curing accelerator is not particularly limited, and is an imidazole such as 2-methylimidazole, an organic phosphorus compound such as triethanolamine, tetraphenylphosphonium / tetraphenylborate, or triphenylphosphine, 1,8- Examples thereof include diazabicyclo [5.4.0] undecene-7 and diazabicycloalkene compounds such as 1,5-diazabicyclo [4.3.0] nonene-5. These compounds may be used alone or in combination of two or more. And it is preferable to set the mixture ratio of this hardening accelerator to the ratio of 0.1 to 1.0 weight% of the whole epoxy resin composition.

  The tablet for semiconductor encapsulation of the present invention is produced, for example, as follows using each of the above components. That is, the above components are blended at a predetermined ratio, dry blended with a mixer or the like, and then kneaded at a resin temperature of 90 to 130 ° C. using a biaxial kneader. Next, the kneaded material discharged from the kneader is rolled into a sheet shape with a calender roll machine or the like so that the sheet density ratio is 98% or more, and then the sheet is air-cooled and pulverized. Next, the tablet for semiconductor sealing intended by compressing the obtained pulverized product to a predetermined tablet height so as to achieve a desired tablet density ratio in a tableting machine, and tableting into a tablet shape. Is manufactured.

As described above, the roll-formed sheet is formed to a sheet density ratio of 98% or more. Then, the time, sheeted and rolled to a thickness 0.2 to 1.0 m m. More specifically, a conventional sheet formed by rolling is usually 2 mm or more in thickness. In this case, the sheet density ratio is about 93 to 97%. In the present invention, however, the sheet has a sheet thickness of 1.0 mm. When the density ratio is 98 to 99% and the sheet thickness is 0.7 to 0.5 mm, the sheet density ratio is 99 to 100%. Therefore, it is particularly preferable to set the sheet thickness to 0.7 mm or less from the relationship of the sheet density ratio . As in this, the sheet density ratio becomes moldable and high density of 98% or more by sheet thickness is rolled to 1.0mm or less, Ya cavities interspersed within kneaded product discharged by the mixer This is because cavities and the like caused by bubbles entrained during transfer to the roll can be efficiently removed by rolling into a sheet in a molten state.

  In order to set the sheet density ratio to 98% or more as described above, other than the sheet thickness being 1.0 mm or less, for example, a method by increasing kneadability, discharging at a high temperature, or the like can be used. Specifically, methods such as depressurization and deaeration treatment in a kneader, extension of the kneading time, and increase in the kneading temperature can be mentioned. The sheet density ratio is measured and calculated as follows. That is, the specific gravity of the sheet was determined by the specific gravity measurement method (based on JIS K6911) obtained from the mass of the obtained sheet in air and the mass in water, and similarly obtained sealing material molding (cured product of resin composition) ) To calculate the sheet density ratio. More specifically, the specific gravity of the sheet is determined by the specific gravity measuring method. On the other hand, the cured product of the resin composition was molded under molding conditions: temperature 175 ° C. × 2 minutes, 6.865 MPa, post-curing 175 ° C. × 5 hours, and the sealing material molded product by the specific gravity measurement method as described above. Find the true specific gravity of Then, from these measured values, the sheet density ratio is calculated by the following formula: sheet density ratio (%) = [(specific gravity of sheet) / (true specific gravity of encapsulant molding)] × 100.

  In addition, for the pulverization of the roll-formed sheet, an ordinary mechanical pulverizer having a hardness equal to or higher than the hardness of the inorganic filler to be blended, for example, a hammer-type pulverizer can be used.

  The particle size distribution of the pulverized resin composition (pulverized product) can be confirmed with a JIS standard sieve. In the present invention, the proportion of the pulverized particles remaining on the 1.0 mm sieve is preferably 50% by weight or less. The preferred lower limit is 7% by weight. That is, when the amount exceeds 50% by weight, even if the above-mentioned sheet density ratio is high, voids remain between the particles, and conversely, voids during molding tend to increase. Therefore, it is preferable that the particle | grains exceeding a particle size of 1.0 mm of the whole ground material are 50 weight% or less.

  Furthermore, it is preferable that the ratio of the pulverized particle | grains which pass a 0.125mm sieve is 10 to 40 weight% of the whole, Most preferably, it is 10 to 25 weight%. Fine particles, such as pulverized particles that pass through a 0.125 mm sieve, fill the space between the large particles and reduce the amount of bubbles taken into the tablet when forming the tablet. . However, when the proportion exceeds 40% by weight, the bulk density is lowered, and the amount of bubbles taken in tends to increase, which makes it difficult to form a tablet. Therefore, it is particularly preferable that particles having a particle size of 0.125 mm or less be suppressed to 25% by weight or less from the relationship between variations in compression pressure and tablet density. Thus, it is preferable that the particle | grains with a particle size of 0.125 mm or less of the whole ground material are 10 to 40 weight%, Especially preferably, it is 10 to 25 weight%.

  The density ratio of the tablet formed by tableting is set to 94% or more and less than 98%. Particularly preferably, it is 96% or more and less than 98%. The reason for setting the tablet density ratio of tableting to less than 98% is as follows. That is, (1) Even if the sheet density is 99 to 100%, in order to make the tablet density 98% or more, very large pressurization is required, which is not possible or preferable in terms of apparatus. (2) From a kneader Volatile components remain in the discharged material, and volatile components are present in the resin composition at the time of tableting, such as moisture absorption during storage due to an increase in surface area due to grinding. If such a resin composition is tableted at a high density of 98% or more, it will be difficult to be degassed and dehumidified later, and it will remain as a void due to difficulty in separating volatile components from the high density layer during resin flow during molding. It is easy. The tablet density ratio is measured and calculated as follows. That is, since the tablet is cylindrical, the bulk specific gravity of the tablet is obtained from the diameter, height and weight of the tablet, and the tablet density ratio is determined by the ratio of the true specific gravity value of the sealing material molded product (cured product of the resin composition). Is calculated. More specifically, the bulk specific gravity of the tablet is obtained as described above, and the true density of the sealing material molding obtained by the above-described method is used to calculate the following formula: tablet density ratio (%) = [(tablet The specific gravity of the tablet is calculated by the following formula.

The pressure at the time of tabletting into tablets by the compression is set to a range of 2 45~784MPa.

  Thus, in the present invention, the formation of internal voids in a semiconductor device formed using a tablet is effectively suppressed by satisfying the above ranges for all values of the sheet density ratio and tablet density ratio. It becomes possible. Therefore, if any one of the above values is out of the setting range, the effect of the present invention cannot be obtained. For example, even if the density ratio of the finally obtained tablet is 97%, it is difficult to suppress the formation of internal voids in the semiconductor device if the sheet density ratio before pulverization is less than 98%.

  If the tablet for semiconductor sealing of this invention is substantially cylindrical shape, the magnitude | size etc. will not specifically limit, However, Usually, it is preferable that it is the range of diameter 7-30mm and height 10-45mm.

  The sealing of the semiconductor element using the thus obtained semiconductor sealing tablet is not particularly limited, and can be performed by a known molding method such as normal transfer molding.

  Next, examples will be described together with comparative examples.

  Each component shown below was prepared.

[Biphenyl type epoxy resin]
Epoxy equivalent 173, melting point 100 ° C.
[Phenol novolac resin]
Hydroxyl equivalent weight 107, melting point 60 ° C
[Curing accelerator]
Triphenylphosphine (Carnauba wax)
[Inorganic filler]
Fused spherical silica powder (average particle size 20μm)
〔Carbon black〕
〔Silane coupling agent〕
γ-glycidoxypropyltrimethoxysilane

[Examples 1-6, Comparative Examples 1-6]
Each component shown in Table 1 below was put into a mixer at the ratio shown in the table and dry blended, and then the mixture was supplied to a biaxial kneader and melt-kneaded at a resin temperature of 110 ° C. Next, the kneaded material discharged from this kneader was formed into a sheet by rolling with a calender roll having a diameter of 150 mm. At this time, the gap of the roll, the pressing pressure, and the like were adjusted so as to obtain a sheet having a thickness shown in Table 2 below. Next, the melt-kneaded product formed into the above-mentioned sheet shape was air-cooled and then pulverized using a hammer mill, and further tableted into a tablet shape. In this tableting, a rotary tableting machine (33 series) manufactured by Kikusui Seisakusho Co., Ltd. performs tableting of tablets continuously while rotating a rotating disk with a plurality of mortars and punches provided in a pair. Was used. And the tablet for semiconductor sealing was produced by compressing so that it might become a desired tablet density ratio.

  For each of the semiconductor sealing tablets thus obtained, the tablet density ratio was measured and calculated according to the method described above. Further, the sheet density ratio at the time of rolling and forming into each of the above sheet shapes was also measured and calculated according to the method described above. The sheet thickness was measured using a caliper after air-cooling a sheet formed and processed. These results are shown in Table 2 and Table 3 below.

  A semiconductor device (20 samples) was produced using the thus obtained semiconductor sealing tablets under the following conditions. Then, the inside of the obtained semiconductor device was observed using an X-ray device, the number of internal voids having a size of 100 μm or more was counted, and the average value of the number of internal voids of 20 semiconductor devices was calculated. The results are shown in Tables 2 and 3 below.

Semiconductor device size: 144 pink quad flat package (144-pin QFP)
20mm x 20mm
Chip size: 7.5mm x 7.5mm
Transfer molding conditions: Thermosetting at 175 ° C. for 90 seconds Molding pressure: 6.865 MPa
Molding machine: Multi-plunger system manufactured by TOWA

[Weight variation]
Prepare 50 tablets (diameter 14mm, target weight 6g), weigh each tablet, examine the variation in weight according to the following criteria, and show the results in Table 2 and Table 3 below. It was shown together.
A: (maximum value−minimum value) / average value <0.3%
○: 0.3% ≦ (maximum value−minimum value) / average value <0.5%
Δ: 0.5% ≦ (maximum value−minimum value) / average value <2.0%
×: 2.0% ≦ (maximum value−minimum value) / average value

(Pressure force index)
The pressing force required at the time of tablet molding was measured in each Example and Comparative Example, and the ratios when the value of Comparative Example 1 was taken as the reference value 1 were also shown in Tables 2 and 3 below.

  As is clear from the above results, the semiconductor device manufactured using a tablet having a tablet density ratio of 94% or more and less than 98% formed by tableting a pulverized product made of a rolled sheet having a sheet density ratio of 98% or more Voids were not formed or very little if formed.

  On the other hand, a semiconductor device manufactured using any one of the tablets having a sheet density ratio of less than 98% or a tablet density ratio of less than 94% and 98% or more has an internal void compared to the embodiment. Many formed.

Claims (3)

A step of preparing a kneaded product of an epoxy resin composition having the following components (A) to (C) as essential components, and the kneaded product having a thickness of 0.2 to 1.0 mm and a sheet density ratio of 98% or more A step of rolling and forming into a sheet shape, and a step of tableting and molding the pulverized product into a tablet shape having a tablet density ratio of 94% or more and less than 98% within a pressure range of 245 to 784 MPa after pulverizing the sheet-like molded body. A method for producing a semiconductor sealing tablet, comprising:
(A) Epoxy resin.
(B) Phenolic resin.
(C) Inorganic filler.   The method for producing a tablet for semiconductor encapsulation according to claim 1, wherein the sheet-shaped molded body has a thickness of 0.5 to 0.7 mm and a sheet density ratio of 99 to 100%.   3. The semiconductor encapsulating material according to claim 1, wherein the pulverized product has a particle size distribution of 50% by weight or less of particles having a particle size exceeding 1.0 mm and 10 to 40% by weight of particles having a particle size of 0.125 mm or less. Tablet manufacturing method.