JPS6325013B2 - - 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 using other curing agents, IC, It is widely used as a resin encapsulation material for semiconductor devices such as 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 that make up the epoxy resin composition, but also various other components have been investigated, and some improvements have been made in the moisture resistance properties at high temperatures and high humidity and the electrical properties at high temperatures. However, epoxy resin compositions are not necessarily sufficient for semiconductor encapsulation, and epoxy resin compositions with excellent moisture resistance and 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 IC 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 between the two and reaches the element. This moisture causes
Trace amounts of water-soluble substances, such as ionic impurities such as chlorine, sodium, and organic acids, as well as unreacted substances with polar groups, are eluted from the cured product of the epoxy resin composition, reach the surface of the semiconductor element, and corrode the aluminum wiring. let (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, the organic acid 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 curing point of the phenolic resin is adjusted. By adding a specific amount of an N-phosphorylimidazole compound to the epoxy resin and phenolic resin, it has excellent curing properties, electrical properties at high temperatures, and moisture resistance properties, and as a result, it can be left for a long time under high temperature and high humidity conditions. The inventors discovered that an epoxy resin composition that does not corrode aluminum wires or cause wire breakage even when the aluminum wires are used, has excellent molding workability, and has high long-term storage stability, led to the completion of the present invention. It is something. Therefore, the present invention provides: (1) a cresol novolac epoxy resin 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; , (2) Softening point is 80-120℃, organic acid content is
100ppm or less, free Na, Cl is 2ppm 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~
(3) total amount of epoxy resin and phenolic resin; (3) total amount of epoxy resin and phenolic resin;
The present invention provides an epoxy resin composition containing an N-phosphorylimidazole compound in an amount of 0.4 to 5 parts by weight per 100 parts by weight, and (4) 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 a material 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, moisture resistance will decrease. 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 in combination 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 from this composition, voids may occur in the molded products, and unfilled , 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 becomes low, which causes poor heat resistance, and if the softening point exceeds 120°C, the melt viscosity of the epoxy resin composition increases, resulting in poor workability. The softening point of the 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. . In the present invention, N is added to the epoxy resin composition containing the above-mentioned epoxy resin and phenol resin.
By adding a -phosphorylimidazole compound, the moisture resistance is improved several times. Examples of N-phosphorylimidazole compounds that are effective in improving the moisture resistance include compounds represented by the following general formula. (However, in the formula, R represents H or a substituted or unsubstituted monovalent hydrocarbon group, and R' represents -OH, imidazolyl-(1)-, -O-alkyl group, or -O-allyl group. ) Specific examples of this N-phosphorylimidazole compound include compounds having the following structure.

【formula】

【formula】

【formula】

[Examples 1-3, Comparative Examples 1-3]

Cresol novolac epoxy resin with epoxy equivalent weight 196 (chlorine ion 1ppm, hydrolyzable chlorine
300ppm, organic acid content 20ppm) 66.2 parts by weight, phenolic novolac 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
Part by weight, 1 part by weight of γ-glycidoxypropyltrimethoxysilane contains N of the type and amount shown in Table 1.
- A composition comprising a phosphorylimidazole compound and 0.7 parts by weight of triphenylphosphine as a curing accelerator is thoroughly mixed, kneaded with heated rolls, cooled, and pulverized to form an epoxy resin composition (implemented). Examples 1 to 3) were obtained. For comparison, the N-phosphorylimidazole compound of the above example was not used, and the first
Epoxy resin compositions (Comparative Examples 1 to 3) were obtained under the same composition and manufacturing conditions as in the above examples, except that the types and amounts of curing accelerators shown in the table were used. The following tests A to C were conducted on these epoxy resin compositions. A. Measurement of volume resistivity ratio 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 at a water vapor pressure of 120°C for 500 hours, and then the dielectric loss tangent (1kHz) was measured according to JIS-K6911. 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 120℃ for 500 hours. , a failure was determined by detecting a disconnection in the aluminum wiring. The results of the above tests are shown in Table 1.

【table】

[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.

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

Epoxy resin compositions (Examples 6 to 8, Comparative Examples 11, 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 according to EMM1 standard, 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 prepared by changing only the blending amount of the N-phosphorylimidazole compound in Example 1, and the above-mentioned C,
Tests D and E were conducted and the results shown in Table 4 were obtained.

[Table] From the results in Table 4, if the amount of N-phosphorylimidazole compound added is too small, no improvement in Al corrosion will be observed, and if it is too large, the spiral flow will be shortened and the Al corrosion rate and molding defect rate will decrease. It was confirmed that an epoxy resin composition with good Al corrosion rate and molding defect rate can be obtained when the blending amount satisfies the range of the present invention.

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.
Use a novolak type phenolic resin with free Na, Cl of 2 ppm or less and free phenol of 1% or less, and the molar ratio of the epoxy group (a) of the epoxy resin to the phenolic hydroxyl group (b) of the phenolic resin. Adjust (a/b) to a range of 0.8 to 1.5 and further N
- Phosphorylimidazole compound per 100 parts by weight of the total amount of the epoxy resin and the phenol resin
An epoxy resin composition characterized in that 0.4 to 5 parts by weight is added. 2. As an inorganic filler, 200 to 200 parts of quartz powder per 100 parts by weight of the total amount of epoxy resin and phenol resin.
500 parts by weight of the epoxy resin composition according to claim 1.