JPS6325011B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to an epoxy resin composition particularly suitable for use in encapsulating semiconductor devices. Problems to be Solved by the Prior Art and the Invention Epoxy resin molding materials generally have superior electrical properties, mechanical properties, adhesive properties, moisture resistance, etc., compared to other thermosetting resins, and It has sufficient fluidity even at low pressures and maintains characteristics such as not deforming or damaging inserts, so it is used as a highly reliable electrical insulation material.
It is widely used for sealing and impregnating electronic components such as ICs, LSIs, diodes, transistors, and resistors. Conventionally, typical curing agents for this epoxy resin molding material include acid anhydrides, aromatic amines, novolac type phenolic resins, etc. Among these, epoxy resin molding materials using novolak type phenolic resin as a curing agent Compared to epoxy resin molding materials that use other curing agents, it has the characteristics of being the best in terms of moisture resistance, reliability, moldability, etc., as well as being non-toxic and inexpensive. Widely used as a resin encapsulation material for semiconductor devices such as ICs, LSIs, diodes, and transistors. However, epoxy resin molding materials that use novolac-type phenolic resin as a curing agent have poor electrical properties at high temperatures, so using this material can reduce the operating temperature to 80°C.
When encapsulating a MOS type semiconductor device with the above characteristics,
This sealing device is used for chip wiring because leakage current flows between the electrodes, causing the chip to no longer exhibit normal semiconductor characteristics. The disadvantages include that the aluminum wire corrodes in a short period of time, causing wire breakage. For this reason, not only the epoxy resin and curing agent constituting the epoxy resin composition, but also various other components have been investigated, and epoxy resin compositions that use organic phosphine compounds as curing accelerators have been developed using other catalysts. It is a component of epoxy resin compositions for semiconductor encapsulation, etc., for reasons such as improved moisture resistance at high temperatures and high humidity and electrical properties at high temperatures compared to when imidazole, tertiary amines, etc. are used. It is often used as a moisture resistant,
Epoxy resin compositions with excellent high-temperature electrical properties are desired. The present invention was made in view of the above circumstances, and an object of the present invention is to provide an epoxy resin composition having excellent moisture resistance and high-temperature electrical properties. Means and Effects for Solving the Problems In order to achieve the above object, the present inventors have conducted various studies and found that the moisture resistance observed when an epoxy resin composition is used for semiconductor encapsulation. We considered the reasons for the poor high-temperature electrical characteristics as shown in A and B below. B. Cause of poor high-temperature electrical properties for semiconductor encapsulation If the encapsulation resin contains trace amounts of ionic impurities or polar substances, these become active and move easily in a high-temperature atmosphere. Furthermore, the sealing resin is in direct contact with the surface of the semiconductor element, but when an electric field is generated on the semiconductor element, the action of the electric field promotes the movement of ionic impurities and polar substances in the resin part that is in contact with the element. As a result, the characteristics of the resin deteriorate at the interface between the element and the resin. As a result, a leakage current occurs between the electrodes of the device, which in turn causes a shoot phenomenon, and eventually the device no longer exhibits normal semiconductor characteristics. (b) Causes of corrosion of aluminum wiring of ICs left in a high temperature and high humidity atmosphere (i) If the adhesiveness between the encapsulating resin and the element and lead frame is poor, Moisture penetrates the interface with the frame and reaches the element. This moisture causes trace amounts of water-soluble substances such as chlorine, sodium, etc. to be removed from the cured epoxy resin composition.
Ionic impurities such as organic acids and unreacted substances with polar groups are eluted, reach the surface of the semiconductor element, and corrode the aluminum wiring. (ii) Since the cured product of the epoxy resin composition for semiconductor devices has hygroscopicity and water permeability, moisture from the outside penetrates into the interior through the cured product in a high-temperature, high-humidity atmosphere, causing damage to the semiconductor device. reach the surface. The aluminum wiring is corroded in the same manner as in (i) below. Therefore, the present inventors have utilized the excellent advantages found in conventional epoxy resin compositions by using a novolac type phenolic resin as a curing agent, while also reducing the moisture resistance and high-temperature electrical properties based on the above (a) and (b). As a result of intensive research into epoxy resin compositions that eliminate these causes as much as possible, we found that it is important to reduce ionic or polar impurities in epoxy resin compositions, and to achieve this goal, it is especially important to reduce the amount of organic acids in epoxy resins. , the amount of chlorine ions and hydrolyzable chlorine, organic acids and free Na in the phenolic resin,
reducing the amount of Cl, the amount of free phenol,
Further, the epoxy equivalent of the epoxy resin, the molar ratio (a/b) of the epoxy group a of the epoxy resin and the phenolic hydroxyl group b of the phenolic resin are adjusted, and the softening point of the phenolic resin is adjusted. By adding and using a specific amount of a specific organic phosphine compound, that is, a compound having a carbonyl group directly bonded to a phosphorus atom, to a phenol resin, it has excellent curing properties, electrical properties at high temperatures, and moisture resistance properties, and as a result, high temperature and high temperature resistance properties are achieved. It was discovered that an epoxy resin composition that does not corrode or break the aluminum wire even if left in a humid environment for a long time, has excellent moldability, and has high long-term storage stability. , which led to the completion of the present invention. Therefore, the present invention provides: (1) a cresol novolac epoxy having an organic acid content of 100 ppm or less, a chlorine ion content of 2 ppm or less, a hydrolyzable chlorine content of 500 ppm or less, and an epoxy equivalent of 180 to 230; Resin, (2) Softening point is 80~120℃, organic acid content is
100 ppm or less, free Na, Cl is 2 ppm or less, free phenol is 1% or less, and the molar ratio (a/b) of the epoxy group a of the epoxy resin and the phenolic hydroxyl group b of the phenolic resin is 0.8 to
Novolac type phenolic resin with a blending amount adjusted within the range of 1.5, (3) having a carbonyl group directly bonded to a phosphorus atom, and the total amount of epoxy resin and phenolic resin
The present invention provides an epoxy resin composition containing an organic phosphine compound in an amount of 0.4 to 5 parts by weight per 100 parts by weight, (4) a curing accelerator if necessary, and (5) an inorganic filler. The present invention will be explained in more detail below. First, the epoxy resin (1) constituting the composition of the present invention has an average structural formula of This is a cresol novolak epoxy resin shown by In this case, the epoxy resin contains organic acid content of 100 ppm or less, more preferably 20 ppm or less, chlorine ion content of 2 ppm or less, more preferably 1 ppm or less, and hydrolyzable chlorine content of 500 ppm or less. The following, more preferably
It is necessary to use one with an epoxy equivalent of 300 ppm or less and an epoxy equivalent of 180 to 230, more preferably 180 to 210. If even one of these conditions is not satisfied, the moisture resistance will be poor. In addition, the above-mentioned novolak type epoxy resin may be used with other epoxy resins, such as glycidyl ether type epoxy resin, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin,
It can be used in combination with alicyclic epoxy resins, these halogenated epoxy resins, and the like. in this case,
It is also preferable to reduce the organic acid content and total chlorine content of these other epoxy resins. Further, the amount of these other epoxy resins used is preferably 50 parts by weight or less per 100 parts by weight of the novolak type epoxy resin. Furthermore, when using the above-mentioned component (1),
There is no problem in using a monoepoxy compound as appropriate, and examples of the monoepoxy compound include styrene oxide, cyclohexene oxide, propylene oxide, methyl glycidyl ether, ethyl glycidyl ether, phenyl glycidyl ether, allyl glycidyl ether, octylene oxide, and dodecene. Examples include oxides. In addition, the novolak type phenolic resin (2) used as the curing agent of the present invention has an average structural formula of This novolak type phenolic resin is obtained by reacting the phenol represented by the formula with formalin using an acid catalyst.Similar to the above-mentioned cresol novolak epoxy resin, this novolak type phenolic resin is free Na,
It is necessary to keep Cl below 2ppm. In addition, if the monomer phenol contained in this composition, that is, the amount of free phenol, exceeds 1%, in addition to having a negative effect on the moisture resistance, when molded products are made with this composition, voids and end-filling may occur in the molded products. , because defects such as whiskers occur, the amount of free phenol mentioned above is 1%.
It is necessary to do the following. Furthermore, the amount of organic acids such as formic acid produced by the Cannitzaro reaction of trace amounts of formaldehyde remaining during the production of this novolac type phenolic resin is also important from the viewpoint of moisture resistance of semiconductors.
Must be 100ppm or less. Furthermore, if the softening point of novolak type phenolic resin becomes less than 80℃,
The Tg will be low, which will result in poor heat resistance, and if the softening point exceeds 120°C, the melt viscosity of the epoxy resin composition will increase, resulting in poor workability, and in both cases, moisture resistance will be poor. The softening point of the novolac type phenolic resin must be 80 to 120°C. In addition, free
A more preferable range for Na and Cl is 2 ppm or less, a more preferable range for the amount of free phenol is 0.3% or less, a more preferable range for the amount of organic acid is 30 ppm or less, and a more preferable range for the softening point of the novolak type phenolic resin is 90%. ~110°C, and by adjusting the temperature within the above range, the object of the present invention can be more reliably achieved. Furthermore, in addition to the novolak type phenolic resin of the present invention, phenol-furfural resin, resorcinol-formaldehyde resin, these organopolysiloxane-modified phenolic resins, natural resin-modified phenolic resins, oil-modified phenolic resins, etc. may be used in combination as appropriate. do not have. In the present invention, an epoxy resin composition containing the above-mentioned epoxy resin or phenol resin has the following general formula in which a carbonyl group is directly bonded to a phosphorus atom. By adding an organic phosphine compound shown in the following, the moisture resistance is improved by several steps. In this case, the organic phosphine compounds used in the present invention include benzoyldiphenylphosphine,
Examples include benzoylphosphine such as tribenzoylphosphine, carbamoylphosphine such as tris(phenylcarbamoyl)phosphine, and one or more of these may be used. Among these, benzoylphosphine and carbamoylphosphine are particularly preferred. The amount of these organic phosphine compounds added is the same as the epoxy resin in (1) above.
0.4 per 100 parts by weight of the total amount of (2) and phenolic resin
The amount is 5 parts by weight, preferably 0.8 to 2.0 parts by weight, and excellent effects for the purpose of the present invention are exhibited at this amount. The curing accelerator (4) is further added to the epoxy resin composition of the present invention, if necessary. Examples of the curing accelerator (4) include triphenylphosphine, tricyclohexylphosphine, tributylphosphine, methyl Organic phosphine compounds such as diphenylphosphine, 1,2-bis(diphenylphosphino)ethane, and bis(diphenylphosphino)methane; Although tertiary amines, imidazoles, etc. can be used, it is particularly desirable to use triphenylphosphine.
The blending amount is 0.5 to 3 per 100 parts by weight of the epoxy resin (1) and the phenol resin (2), especially
The amount is preferably 0.8 to 2 parts by weight. Examples of the inorganic filler (5) used in the present invention include quartz powder, alumina powder, talc, glass fiber, and antimony trioxide, and among these, quartz powder is most preferred. This quartz powder may be either amorphous or crystalline, or a mixture thereof, and may be natural or synthetic. When using equipment to protect against alpha rays, it is preferable to use powdered or spherical synthetic quartz with low content of uranium, thorium, etc.
Crystalline material with a SiO ₂ content of 98% or more or fused quartz in which SiO ₂ is once melted is preferable. When using quartz powder as an inorganic filler, the preferred average particle diameter range of quartz powder is 1 to 30 μm;
A more preferable range is 5 to 20 μm, and the amount of quartz powder blended is 200 to 500 parts by weight, more preferably 230 parts by weight, per 100 parts by weight of the epoxy resin in (1) and the phenol resin in (2) above. It is desirable to set it to 400 parts by weight. Quartz powder having the above particle size distribution can be obtained by crushing and classifying silica or fused silica, and spherical silica can be obtained by crushing silica or synthetic quartz and treating it in an oxyhydrogen flame. The particle size can be adjusted by classification if necessary. The composition of the present invention may further contain various additives depending on its purpose, use, etc., if necessary. For example, waxes, mold release agents such as fatty acids such as stearic acid and their metal salts, pigments such as carbon black, dyes, flame retardants, surface treatment agents (γ-glycidoxypropyltrimethoxysilane, etc.), aging There is no problem in blending an inhibitor, a silicone-based flexibility imparting agent, and other additives. The composition of the present invention can be obtained by a method such as uniformly stirring and mixing the required amounts of the above-mentioned components, kneading with a roll or kneader preheated to 70 to 95°C, cooling, and pulverizing. can. Note that there is no particular restriction on the order of blending the components. The epoxy resin composition of the present invention is used for sealing semiconductor devices such as ICs, LSIs, transistors, thyristors, and diodes, and for manufacturing printed circuit boards. In the case of sealing the semiconductor device, conventionally used molding methods such as transfer molding, injection molding, and casting can be used. In this case, the molding temperature of the epoxy resin composition is preferably 150 to 180°C, and the post-curing is preferably carried out at 150 to 180°C for 2 to 16 hours. Effects of the Invention As explained above, the present invention provides an epoxy resin composition containing an epoxy resin, a phenol resin as a curing agent, an organic phosphine compound according to the present invention, and an inorganic filler. We use a cresol novolac epoxy resin with a content of 100 ppm or less, a chlorine ion content of 2 ppm or less, a hydrolyzable chlorine content of 500 ppm or less, and an epoxy equivalent of 180 to 230, and a softening point of 80 as a phenolic resin. ~120°C, using a novolak type phenolic resin with an organic acid content of 100 ppm or less, free Na and Cl content of 2 ppm or less, and free phenol of 1% or less, and the epoxy group a of the epoxy resin and the phenol. The molar ratio (a/b) of the resin to the phenolic hydroxyl group b is 0.8 to
1.5, and further add an organic phosphine compound having a carbonyl group directly bonded to a phosphorus atom in the total amount of the epoxy resin and the phenolic resin.
By adding 0.4 to 5 parts by weight per 100 parts by weight, an epoxy resin composition can be obtained which has excellent moisture resistance and high-temperature electrical properties and is suitably used for encapsulating semiconductor devices. EXAMPLES Hereinafter, the present invention will be specifically explained by showing examples and comparative examples, but the present invention is not limited to the following examples. [Examples 1 to 3, Comparative Examples 1 to 3] Cresol novolak epoxy resin with an epoxy equivalent of 196 (chlorine ion 1 ppm, hydrolyzable chlorine
300ppm, organic acid content 20ppm) 66.2 parts by weight, novolac type phenolic resin with a softening point of 100℃ (organic acid content 10ppm, Na ion, Cl ion each)
1ppm, free phenol 0.1%) 33.8 parts by weight,
30 parts by weight of antimony trioxide, 230 parts by weight of fused quartz,
1 part by weight of carnauba wax, 1 part of carbon black
Thoroughly mix a composition consisting of 1 part by weight of γ-glycidoxypropyltrimethoxysilane, carbamoylphosphine or benzoylphosphine of the type and amount shown in Table 1, and a curing accelerator. After that, the epoxy resin compositions (Examples 1-
3) was obtained. Also, for comparison, carbamoylphosphine,
Alternatively, epoxy resin compositions (Comparative Examples 1 to 3) were obtained under the same composition and preparation conditions as the above-mentioned epoxy compositions, except that an organic phosphine compound according to the present invention such as benzoylphosphine was not used. Regarding these epoxy resin compositions, the following A
-C tests were conducted. A. Measurement of volume resistivity A test in which a disk with a diameter of 7 cm and a thickness of 2 mm was made by molding at a molding temperature of 175°C, a molding pressure of 70 Kg/cm ² , and a molding time of 2 minutes, and this was post-cured at 180°C for 4 hours. The value of the piece when heated at 150°C was measured according to JIS-K6911. B. Measurement of moisture resistance characteristics A disk with a diameter of 5 cm and a thickness of 3 mm obtained under the same molding and post-curing conditions as in A above was held in steam at 120°C for 500 hours, and then the dielectric loss tangent (1kHz) was measured according to JIS-K6911. It was measured. C Al corrosion test 100 14-pin ICs with Al wiring on the chip were molded using transfer molding material, the molded products were post-cured at 180℃ for 4 hours, and then left in steam at 10℃ for 500 hours. , a failure was determined by detecting a break in the aluminum wiring. The results of the above tests are shown in Table 1.

[Examples 4 and 5, Comparative Examples 4 to 10]

An epoxy resin composition was prepared using the same additives, blending ratio, and manufacturing conditions as in Example 1, except that the purity of the cresol novolac epoxy resin and novolac type phenol resin used in Example 1 was as shown in Table 2. (Examples 4 and 5 and Comparative Example 4~
10) was made and subjected to the Al corrosion test in C above and the molding failure rate test in D below. D Measurement of molding defect rate 14PIN IC made of 100 pieces with a transfer molding machine
Ten shots were molded using the mold, and the appearance defect rate (defects such as voids, unfilled areas, snake eyes, etc.) was measured. The test results for C and D above are shown in Table 2.

【table】

[Examples 6 to 8, Comparative Examples 11 and 12]

Epoxy resin compositions (Examples 6 to 8, Comparative Examples 11 and 12 ), and the molding failure rate of D, the secondary transition temperature Tg, and the spiral flow of E below were measured. E Spiral Flow Using a mold that complies with EMMI standards, 175℃, 70
Measured under the condition of Kg/ ^cm2 . The above measurement results are shown in Table 3.

[Examples 9 to 11, Comparative Examples 13 and 14]

Epoxy resin compositions (Examples 9 to 11, Comparative Examples 13 and 14) were made by changing only the amount of tris(phenylcarbamoyl)phosphine in Example 3, and the above-mentioned tests C, D, and E were conducted. The results shown in Table 4 were obtained.

[Table] From the results in Table 4, it is clear that if the amount of tris(phenylcarbamoyl)phosphine (organophosphine compound according to the present invention) is too small, no improvement in Al corrosion will be observed, and if it is too large, the spiral flow will be shortened. Therefore, both the Al corrosion rate and the molding defect rate increase, but in the case of a blending amount that satisfies the scope of the present invention,
It was confirmed that an epoxy resin composition with good Al corrosion rate and molding defect rate could be obtained.

Claims (1)

[Claims] 1. An epoxy resin composition containing an epoxy resin, a phenolic resin as a hardening agent, and an inorganic filler, wherein the epoxy resin has an organic acid content of 100 ppm or less and a chlorine ion content of 2 ppm. Below, a cresol novolac epoxy resin with a hydrolyzable chlorine content of 500 ppm or less and an epoxy equivalent of 180 to 230 is used, a phenol resin with a softening point of 80 to 120°C, and an organic acid content of 100 ppm or less.
In addition to using a novolac type phenolic resin with free Na and Cl of 2 ppm or less and free phenol of 1% or less, the epoxy group a of the epoxy resin,
The molar ratio (a/b) of the phenolic hydroxyl group b of the phenolic resin is adjusted to a range of 0.8 to 1.5, and an organic phosphine compound having a carbonyl group directly bonded to a phosphorus atom is added to the epoxy resin and the phenolic resin. An epoxy resin composition characterized in that 0.4 to 5 parts by weight are added per 100 parts by weight of the total amount. 2. The composition according to claim 1, wherein benzoylphosphine or carbamoylphosphine is used as the organic phosphine compound. 3. As an inorganic filler, quartz powder is used in an amount of 200 to 100 parts by weight of the total amount of epoxy resin and phenol resin.
500 parts by weight of the composition according to claim 1 or 2.