JP4543695B2 - Coated carbon material powder and method for producing the same - Google Patents

Description

  The present invention relates to coating of carbon material powder for coloring semiconductor or electrical / electronic molding materials.

Molded products for electrical and electronic use and molding materials for semiconductor encapsulation are colored black with carbon material powder called carbon black or acetylene black, etc. In mounting on a flexible printed circuit, an accident that carbon black agglomerates short-circuit between wiring pitches has become apparent, and urgent countermeasures are required.
Specifically, the primary particle diameter of carbon black is very fine particles of 10 to several tens of nanometers and is usually not a single particle but agglomerated in a chain or a lump. Such carbon powder primary agglomerates themselves are materials that have the handling-like difficulty of being easily scattered and agglomerated, and care must be taken not to cause scattering when kneading and dispersing into a resin. While handling, various dispersion treatments are taken to improve the non-uniform state and prevent aggregation. This dispersion treatment is mainly carried out by optimizing the mixing conditions and kneading conditions of the raw materials, but it is a difficult treatment, and once dispersed carbon black also agglomerates again during melt hardening. As a result, when used for semiconductor elements with protruding electrode parts such as flip chip and wafer level CSP, carbon black aggregates between wiring pitches and causes a short circuit accident, used as an underfill material In such a case, problems such as a short circuit between the semiconductor element and the wiring board are becoming serious. At present, the distance between the protruding electrodes is a few tens of μm, and it is about 10 μm in the future. Further, the gap between the flip chip and the wiring board is expected to be 20 μm in the future from 50 to 100 μm at present. At present, carbon black aggregated particles of 50 μm or more are present after curing, and various attempts are made to reduce the dispersion diameter by various pretreatments, but they have not been completely solved.

  Basically, carbon black is a conductive carbon material, and there is no change in the situation where carbon particles, which are conductive particles, are dispersed in a molding material that requires uniform insulation. It is said that the semiconductor wiring scale is aimed at submicron from micron size, and in this case, the carbon black, which is a conductive particle, contacts between two electrodes at the same time, no matter how suitable the processing is. In this case, it becomes an unavoidable problem to become a contact for short circuit. Examples of using black inorganic oxides instead of carbon black have been reported, but these inorganic oxides are not only insufficient in insulation level but also a source of ionic impurities, Does not meet the necessary and sufficient requirements.

A short-circuiting accident between thin wires due to agglomeration of carbon material powder for coloring such as carbon black cannot be detected by, for example, internal foreign matter inspection using soft X-rays. At present, the only detection method is an energization test at a practical applied voltage. Absent. An application has also been filed for an alternative inspection method (see, for example, Patent Document 1), but it is not perfect, and of course it cannot prevent the occurrence of defective products. For this reason, methods for blending colored raw materials that do not generate agglomerates have been studied (see, for example, Patent Documents 2 and 3), but it is difficult to say that a decisive measure has been reached.
Based on such a background, it has been necessary to develop a technique for insulating a carbon material powder for coloring such as carbon black with a stable resin film.

JP 2001-027637 A (pages 2 to 4) JP 2001-002895 A (pages 2 to 4) JP 2002-363379 A (pages 2 to 4)

  The object of the present invention is to solve obstacles such as a short circuit of a wiring circuit due to the conductivity of the carbon material itself in a carbon material powder such as carbon black used for coloring molded articles and molding materials for semiconductor encapsulation. To do.

The above object is achieved by the present invention described in (1) below.
(1) A method for producing a carbon material powder having a surface coated with polyimide and having a particle size of 10 μm or less , comprising tetracarboxylic dianhydride (I) and diamine (II) coexisting with carbon powder (III) Then, the solution reacted in the organic solvent (IV) was discharged in the form of droplets into the solvent (V) that does not dissolve the polyamic acid to obtain a polyamic acid coating of carbon powder. A method for producing a polyimide-coated carbon material powder that is heated and polyimideized .

  According to the present invention, it is possible to obtain a carbon powder for coloring a semiconductor or a molding material for electric / electronic use that does not cause a failure such as a short circuit without impairing conventional functions.

The best mode for carrying out the present invention is that the coloring carbon material powder is completely insulated from adjacent particles. As a means for expressing the insulating properties of such powder, when the insulating properties are measured by compression molding, no electrical conductivity is exhibited even though carbon material particles are contained. Similarly, when blended as a filler, the conductivity dependence on the blending ratio is not observed. The particles need to be coated to such a state that does not exhibit conductivity.
Furthermore, the particle size is ideally equivalent to the original particle size of the colorant. Carbon black is a particle in which primary particles of several nanometers to several tens of nanometers are combined in a chain or aggregated, and the particle aggregation size before blending ranges from 100 μ to several 100 μm. The effect as a colorant is exhibited when the aggregated particles are dissolved and dispersed with a smaller aggregate size. Such an aggregated particle diameter is visually recognized at a microscope level is 10 μm, and if the particle diameter is smaller than that, it is considered that uniform coloring is performed.
Furthermore, since the particle size is sufficiently smaller than the distance between the pins of the shrinking device, even if the particles of the polyimide-coated carbon material powder aggregate and contact between the pins, the adjacent particles are insulated. There is no possibility of a short circuit accident.
In order to obtain such a coated carbon material powder, the following method is required. That is, carbon material powder (III) such as carbon black is dispersed in advance in a solution of polyamic acid (for example, a mixture of tetracarboxylic dianhydride (I) and diamine (II)). Discharge the polyamic acid into a solvent (V) that does not dissolve it in the form of droplets to obtain a polyamic acid coating of carbon powder and heat it to polyimidize to obtain a polyimide-coated carbon powder. Can do. The polyimide-coated carbon black thus provided can be adjusted to an appropriate particle size by air sieving or the like. In this case, it is preferable to remove particles of 10 μm or more.

Hereinafter, the production method of the carbon material powder insulated and coated with the polyimide of the present invention will be described in detail.
Carbon black is called acetylene black or furnace black depending on the production method and raw materials, but it is either a developed or undeveloped graphite structure when classified by chemical structure. This is due to differences in manufacturing conditions such as whether a graphitizable raw material such as pitch or fossil fuel is used as a raw material or a non-graphitizable raw material such as a resin, or whether the firing temperature is 2800 ° C. or higher. Derived from.
Even when a non-graphitizing raw material is used or pitch coke, which is an easily graphitizing raw material, is used, a carbon material in an amorphous glass state called so-called glassy carbon having a firing temperature of 2800 ° C. or lower The carbon six-membered ring, which is the precursor of the structure, has been completed, so there is no difference in basic electrical conductivity. Therefore, for the fine carbon materials collectively called carbon black, Regardless of whether or not graphitization, that is, graphitization is progressing, it has conductivity and can cause a short circuit.
Classifying from the final carbon structure, the typical structure is a graphitized carbon black that has developed a graphitized structure, and an amorphous carbon carbon black that has been carbonized without forming a graphite structure. It can be said that carbon black as a mixture in which the amorphous carbon structure and the graphite structure are distributed at an arbitrary ratio exists between the two electrodes. The more the graphitized structure is developed, the more anisotropy appears in the conductivity, and the isotropic carbon becomes more isotropic. Carbon black is commercially available as a primary particle from a size of 10 nm, but due to the strong hydrophobicity and the influence of the surface of the fine particles, it is in an aggregated state from several μm to several mm in size, and is handled as aggregated particles. It is used as various industrial raw materials such as pigments and fillers.

  Due to its excellent heat resistance, polyimide is used in various applications that require high reliability, such as a photoresist for semiconductors, an adhesive in an assembly process, or a base film of a flexible printed circuit board. Since the thermal deformation temperature of polyimide itself is far higher than the molding temperature of general thermosetting resin molding materials such as epoxy and phenol, for example, once carbon black is coated with polyimide, the molding material melts and flows. Even in the molding temperature range, the surface coat does not flow out. That is, there is no fear that the surface of the carbon black is exposed and short-circuited.

One production method of carbon black coated with the polyimide of the present invention will be described.
For example, diamine (II) is dissolved in an organic solvent (IV) such as a mixed solvent of NMP (normal 2-methylpyrrolidone) / xylene, and carbon black is added to obtain a suspension state. When tetracarboxylic dianhydride (I) is added while refluxing, the reaction of polyamide oxidation proceeds and mixing of the produced polyamic acid and carbon black proceeds. The order of dissolution and addition of diamine (II) and tetracarboxylic dianhydride (I) is not particularly limited, but this is because a suspension is created by adding carbon black to the raw material side to be dissolved first. In order not to increase the viscosity in this case, the side having the lower solution viscosity may be the side to be dissolved first.
When this mixture is dropped into a solvent (V) that does not dissolve the polyamic acid while taking measures for atomization of the liquid droplets, for example, in water, when the polyamic acid is precipitated, the carbon black particles are hydrophobic and resistant to the solvent. Due to the difference in affinity, it is dispersed in the polyamic acid droplets, and composite droplets are deposited as if they were coated with polyamic acid on carbon black or an aggregate thereof.
At this time, if the atomization operation is performed using, for example, ultrasonic vibration, a mechanism such as agitation or collision, such as a homogenizer, the mixed droplet diameter of the polyamic acid carbon black can be set to an under micron size. .
When the polyamic acid carbon black mixture collected by precipitation is dynamically heated and dried using, for example, a fluidized tank, the polyamic acid is imidized by a dehydration condensation reaction to obtain polyimide-coated carbon black.

The polyimide in the coating film state thus obtained can be confirmed to have a high molecular weight by weight average molecular weight measurement by GPC measurement in terms of polystyrene. For example, when the weight average molecular weight exceeds 100,000, Its softening point is 350 ° C. or higher.
Therefore, the polyimide-coated carbon black surface layer polyimide produced in this way has a softening point in the region higher than the manufacturing temperature in the molding material process and the molding temperature. The surface of the resin is not exposed, and the blackness of the appearance of the particles is maintained while the insulating property is maintained, so that it can be used as a colorant for the molding material in the same manner as ordinary carbon black.

[Molding materials]
The polyimide-coated carbon black produced in the present invention can be used in the same manner as conventional carbon black as a colorant such as a thermosetting or thermoplastic molding material or an underfill material. The thermosetting resin may be an epoxy resin, a phenol resin, a thermosetting resin such as a diallyl phthalate resin or a polyester resin, and may be used by mixing them as necessary. As long as the heat distortion temperature is not higher than polyimide, such as PBT, it can be used without particular limitation.
For example, epoxy resins may be solid or liquid at room temperature, such as various biphenyl type epoxy resins, bisphenol type epoxy resins, alicyclic epoxy resins, allylated bisphenol type epoxy polyfunctional epoxy resins, etc. Can be given. The curing agent is not particularly limited, and various phenol resins, acid anhydrides, amines, phthalic acids and the like can be used, and these can be used alone or in combination of two or more. As the phenolic resin, a novolak resin or a resol type resin is used as necessary, and a hexamethylenetetramine as a curing agent or a curing accelerator is used as necessary. Other thermosetting resins are not particularly limited, and can be effectively used as long as they are resins used for insulation protection such as molding materials and adhesives.

EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these. Example 1
1.95 g of diamine (4,4 ′ diaminodiphenyl ether: DPE) was added to a mixed solvent in which 50 g of xylene was added to 200 g of NMP, and dissolved while heating at 60 ° C. To this solution, 100 g of carbon black (Denka Black manufactured by Denki Kagaku Kogyo) was added, and a slurry in which carbon black was uniformly dispersed was prepared by stirring.
While adding 3.05 g of tetracarboxylic dianhydride (oxydiphthalic anhydride: ODPA) to this slurry, stirring was performed to obtain a slurry in which carbon black was dispersed in the polyamic acid solution. Reflux at reflux temperature for 1 hour.
Next, when this slurry was discharged into cold water at 8 ° C. with an ultrasonic nozzle, droplets of the polyamic acid slurry were deposited and collected by filtration and subjected to centrifugal dehydration.
The dehydrated and recovered particles were heated to 250 ° C. under a nitrogen gas atmosphere in a hot air fluidized drying furnace.
Sample A was obtained by removing particles of 10 μm or more from the obtained polyimide-coated carbon black with an empty sieve.

Example 2
11.69 g of diamine (4,4 ′ diaminodiphenyl ether: DPE) was added to a mixed solvent in which 50 g of xylene was added to 200 g of NMP, and dissolved while heating at 60 ° C. To this solution, 100 g of carbon black (Denka Black manufactured by Denki Kagaku Kogyo) was added, and a slurry in which carbon black was uniformly dispersed was prepared by stirring.
While adding 18.31 g of tetracarboxylic dianhydride (oxydiphthalic anhydride: ODPA) to this slurry, stirring was performed to obtain a slurry in which carbon black was dispersed in the polyamic acid solution. Reflux at reflux temperature for 1 hour.
Next, when this slurry was discharged into cold water at 8 ° C. with an ultrasonic nozzle, droplets of the polyamic acid slurry were deposited and collected by filtration and subjected to centrifugal dehydration.
The dehydrated and recovered particles were heated to 250 ° C. under a nitrogen gas atmosphere in a hot air fluidized drying furnace.
Sample B was obtained by removing particles of 10 μm or more from the obtained polyimide-coated carbon black with an empty sieve.

Example 3
11.80 g of diamine (3,3′diaminobenzophenone) was added to a mixed solvent in which 50 g of xylene was added to 200 g of NMP, and dissolved while heating at 60 ° C. To this solution, 100 g of carbon black (Denka Black manufactured by Denki Kagaku Kogyo) was added, and a slurry in which carbon black was uniformly dispersed was prepared by stirring.
To this slurry, tetracarboxylic dianhydride (benzophenone-3,4,3 ′, 4 ′
While adding 18.20 g of tetracarboxylic dianhydride (BTDA), a slurry in which carbon black was dispersed in the polyamic acid solution was obtained by stirring and refluxed at the reflux temperature of xylene for 1 hour.
Next, when this slurry was discharged into cold water at 8 ° C. with an ultrasonic nozzle, droplets of the polyamic acid slurry were deposited and collected by filtration and subjected to centrifugal dehydration.
The dehydrated and recovered particles were heated to 250 ° C. under a nitrogen gas atmosphere in a hot air fluidized drying furnace.
Sample C was obtained by removing particles of 10 μm or more from the obtained polyimide-coated carbon black with an empty sieve.

Reference example 1
In the same manner as in Example 1, Sample D was obtained by a method in which the produced polyimide-coated carbon black was not removed with a particle size of 10 μm or more by an empty sieve.

Comparative Example 1
As in Example 1, 1.95 g of diamine (4,4 ′ diaminodiphenyl ether: DPE) was added to a mixed solvent in which 50 g of xylene was added to 200 g of NMP, and dissolved while heating at 60 ° C. To this solution, 100 g of carbon black (Denka Black manufactured by Denki Kagaku Kogyo) was added, and a slurry in which carbon black was uniformly dispersed was prepared by stirring.
While adding 3.05 g of tetracarboxylic dianhydride (oxydiphthalic anhydride: ODPA) to this slurry, stirring was performed to obtain a slurry in which carbon black was dispersed in the polyamic acid solution. Reflux at reflux temperature for 1 hour.
Next, an attempt was made to directly produce a polyimide-coated carbon black from the slurry using a spray dryer. However, due to the high boiling point of NMP, sufficient drying could not be performed, and the particles were fused and aggregated. (Sample E)

  The particle diameters of the obtained samples A, B, C and D are shown in comparison with Table-1.

Biphenyl type epoxy resin (manufactured by Japan Epoxy Resin Co., Ltd., YX4000H,
Melting point 105 ° C., epoxy equivalent 195 g / eq) 61.64 parts by weight Phenol novolac resin (softening point 65 ° C., hydroxyl group equivalent 104 g / eq)
34.24 parts by weight Triphenylphosphine 1.37 parts by weight Carnauba wax 2.74 parts by weight were mixed in a 90 ° C. mixer for 1 minute, immediately taken out, cooled and pulverized to prepare a master batch.
This master batch and polyimide coated carbon black prototypes (A), (B), (C
) Each polyimide coated carbon black prototype: parts by weight of masterbatch
70.0 parts by weight: 30.0 parts by weight
60.0 parts by weight: 40.0 parts by weight
The mixture was mixed at a ratio of 50.0 parts by weight: 50.0 parts by weight, kneaded with a 90 ° C. mixer for 3 minutes, and then cooled and ground to obtain a molding material.
By using this molding material, compression molding at 175 ° C. for 2 minutes was performed to JIS K-69.
11 A disk for measuring electrical resistance corresponding to 11 was molded and the electrical resistivity was measured.

Reference example 2
In the same manner as described above, a resin masterbatch was prepared, then silica was blended and molded, and the insulation was measured.
Biphenyl type epoxy resin (manufactured by Japan Epoxy Resin Co., Ltd., YX4000H,
Melting point 105 ° C., epoxy equivalent 195 g / eq) 61.64 parts by weight Phenol novolac resin (softening point 65 ° C., hydroxyl group equivalent 104 g / eq)
34.24 parts by weight Triphenylphosphine 1.37 parts by weight Carnauba wax 2.74 parts by weight were mixed in a 90 ° C. mixer for 1 minute, immediately taken out, cooled and pulverized to prepare a master batch.
This masterbatch and Electrochemical Industry silica
Silica: parts by weight of masterbatch
70.0 parts by weight: 30.0 parts by weight
60.0 parts by weight: 40.0 parts by weight
The mixture was mixed at a ratio of 50.0 parts by weight: 50.0 parts by weight, kneaded with a 90 ° C. mixer for 3 minutes, cooled and pulverized to obtain a molding material.
By using this molding material, compression molding at 175 ° C. for 2 minutes was performed to JIS K-69.
11 A disk for measuring electrical resistance corresponding to 11 was molded and the electrical resistivity was measured.

Comparative Example 2
Similar to the insulation evaluation of the polyimide coated carbon black prototype, a resin masterbatch was prepared, carbon black was blended and molded, and the conductivity was measured.
Biphenyl type epoxy resin (manufactured by Japan Epoxy Resin Co., Ltd., YX4000H,
Melting point 105 ° C., epoxy equivalent 195 g / eq) 61.64 parts by weight Phenol novolac resin (softening point 65 ° C., hydroxyl group equivalent 104 g / eq)
34.24 parts by weight Triphenylphosphine 1.37 parts by weight Carnauba wax 2.74 parts by weight were mixed in a 90 ° C. mixer for 1 minute, immediately taken out, cooled and pulverized to prepare a master batch.
This masterbatch and carbon black (Denka Black manufactured by Denki Kagaku Kogyo)
Carbon black: Master batch weight ratio
70.0 parts by weight: 30.0 parts by weight
60.0 parts by weight: 40.0 parts by weight
The mixture was mixed at a ratio of 50.0 parts by weight: 50.0 parts by weight, kneaded with a 90 ° C. mixer for 3 minutes, cooled and pulverized to obtain a molding material.
By using this molding material, compression molding at 175 ° C. for 2 minutes was performed to JIS K-69.
11 A disk for measuring electrical resistance corresponding to 11 was molded and the electrical resistivity was measured.

These insulation comparison data are shown in Table-2.
The volume resistivity of glassy carbon or graphite is approximately 1 × 10 mΩ · cm. Carbon black is a mixture of glassy carbon and graphite. In order to show the same electrical conductivity, carbon black increases its blending ratio and becomes a molding material, and shows conductivity as the carbon black blending ratio increases. It becomes like this. Moreover, in the example using the silica which is an insulator, and the polyimide coat carbon black of the present invention, as shown in Table 2, the resistivity of the epoxy resin is 1 × 10 ¹⁶ Ω · cm or more which is the original resistivity. Only by showing, the increase tendency of the conductivity with the increase in the blending ratio was not observed. In other words, the conductive carbon black can be used as an insulator by being coated with polyimide.

Example 4
Using the prototype polyimide-coated carbon black sample A, a molding material was formed with the following composition, and the molded material was evaluated.

Polyimide coated carbon black prototype (A) 0.4 parts by weight Spherical fused silica powder (manufactured by Denki Kagaku Kogyo, average particle size 22 μm, maximum particle size 75 μm)
85.0 parts by weight Biphenyl type epoxy resin (manufactured by Japan Epoxy Resin Co., Ltd., YX4000H,
Melting point 105 ° C., epoxy equivalent 195 g / eq) 9.0 parts by weight Phenol novolac resin (softening point 65 ° C., hydroxyl group equivalent 104 g / eq)
5.0 parts by weight Triphenylphosphine 0.2 parts by weight Carnauba wax 0.4 parts by weight were mixed with a mixer, kneaded with a 90 ° C. heating roll for 3 minutes, and cooled and ground to obtain a molding material.

Reference example 3
In Example 4, a molding material was obtained in the same manner except that Sample D containing particles of 10 μm or more prepared in Reference Example 1 was used instead of Sample A.

Comparative Example 3
This is a conventional method in which carbon black is directly blended with a raw material powder as a colorant. In Example 4, instead of 0.4 parts by weight of the polyimide-coated carbon black prototype (A), carbon black (electrochemical industry) A molding material was obtained in the same manner as in Example 4, except that 0.3 parts by weight of Denka Black (manufactured by Denka Black Co., Ltd.) was used and the amount of spherical fused silica powder was corrected.

Carbon black 0.3 part by weight Spherical fused silica powder (manufactured by Denki Kagaku Kogyo, average particle size 22 μm, maximum particle size 75 μm)
85.1 parts by weight Biphenyl type epoxy resin (manufactured by Japan Epoxy Resin Co., Ltd., YX4000H,
Melting point 105 ° C., epoxy equivalent 195 g / eq) 9.0 parts by weight Phenol novolac resin (softening point 65 ° C., hydroxyl group equivalent 104 g / eq)
5.0 parts by weight Triphenylphosphine 0.2 parts by weight Carnauba wax 0.4 parts by weight were mixed with a mixer, kneaded with a 90 ° C. heating roll for 3 minutes, and cooled and ground to obtain a molding material.

[Observation of carbon black aggregates]
Evaluation of agglomerates: Using a molding material of Example 4, Reference Example 3 and Comparative Example 3 on a low-pressure transfer molding machine, a disk having a mold temperature of 175 ° C., an injection pressure of 6.9 MPa, a holding time of 120 seconds, and a disk of 100 mmφ Was molded. This surface was polished, and the polished surface was observed at 20 locations with a fluorescence microscope (Olympus, BX51M-53MF), and the maximum diameter and the number of aggregated particles of 50 μm or more were counted.
In the molding material using polyimide-coated carbon black, agglomerates were observed in the molded product, similarly to the molding material in the case of using carbon black as in the past. Contrary to the fact that carbon black aggregates are expected to have electrical conductivity, it has been confirmed that the polyimide-coated carbon black of the present invention does not exhibit electrical conductivity even when aggregated. And safe.

[General physical property comparison]
Regarding the comparison of general physical properties, there was no difference from the conventional products using carbon black.

  The carbon material for coloring such as carbon black insulated by the polyimide coating of the present invention is a technique for preventing troubles such as short circuit at the time of aggregation, and troubles such as short circuit caused by carbon black are a problem. It is useful as a raw material to be applied to various fields, for example, thermosetting resin compositions for semiconductors and electrical / electronic applications.

Claims (1)

A method for producing a carbon material powder having a surface coated with polyimide and having a particle size of 10 μm or less , comprising tetracarboxylic dianhydride (I) and diamine (II) in the presence of carbon powder (III) The solution reacted in the solvent (IV) was discharged in the form of droplets into the solvent (V) that does not dissolve the polyamic acid to obtain a polyamic acid coating of carbon powder, which was then heated, A method for producing a polyimide-coated carbon material powder to be polyimideized .