JP4966123B2 - Liquid epoxy resin composition for sealing and semiconductor device - Google Patents

Description

  The present invention relates to a sealing liquid epoxy resin composition and a semiconductor device.

  In recent years, resin-encapsulated semiconductor devices have a tendency toward higher density, higher integration, and higher speed of operation, and there is a demand for semiconductor chip packages that can be made smaller and thinner than conventional packages. Therefore, flip chip packages are attracting attention as a means of meeting such demands.

  In the flip chip package, a metal electrode called a bump is directly formed on an external connection pad of a semiconductor chip, and the bump electrode is used to connect and mount on a wiring board face down. Further, the gap between the semiconductor chip and the wiring board is filled with a resin called underfill. The underfill has functions such as relieving the stress at the solder joint caused by the difference in thermal expansion coefficient between the semiconductor chip and the wiring board, and ensuring moisture resistance and airtightness.

  Because of this structure, the mounting area can be almost the same as that of the semiconductor chip, and the bump height is usually as low as several tens of μm, so there is no need to encapsulate the wires as in the case of wire bonding connection. The height after mounting can also be lowered, and it is possible to meet demands for downsizing, thinning, and the like.

  Conventionally, as an underfill material used for a flip chip package, a liquid epoxy resin composition is typically used (see Patent Documents 1 to 3), but in the market for flip chip package underfill, In order to further improve the reliability, a reduction in stress is desired. The main approaches for lowering stress include lower glass transition temperature, lower linear expansion coefficient, lower elastic modulus, etc., but lower glass transition temperature is not suitable for bump protection. However, there is a problem that there is a restriction on the material viscosity in reducing the linear expansion coefficient, and it is considered that lowering the elastic modulus is the most effective method for further reducing the stress of the underfill.

Conventionally, as a method for reducing the elastic modulus of the underfill, it has been generally performed to blend silicone rubber, silicone oil, urethane rubber or the like into a liquid epoxy resin composition.
Japanese Patent No. 3038623 Japanese Patent Laid-Open No. 2007-9188 JP 2003-183351 A

  However, since these materials such as silicone rubber are not so compatible with the liquid epoxy resin, other physical properties of the underfill material may be affected.

  The present invention has been made in view of the circumstances as described above, and can reduce the stress of the underfill without affecting other physical properties and can improve the reliability of the package. It is an object to provide a liquid epoxy resin composition for use and a semiconductor device using the same.

  The present invention is characterized by the following in order to solve the above problems.

1stly, the liquid epoxy resin composition for sealing of this invention is for underfills (except the method of apply | coating to the wafer in which many semiconductor elements which have a solder bump were formed, and setting it as a B-stage). Liquid epoxy resin composition for sealing , epoxy resin solid at room temperature selected from bisphenol A type epoxy resin , O-cresol novolak type epoxy resin and biphenyl type epoxy resin which is liquid at normal temperature, acid anhydride curing agent, curing accelerator, and it contains spherical fused silica as the inorganic filler, the content of solid epoxy resin at normal temperature, 15 to 50 wt% based on the total weight of the epoxy resin, the molten globular The average particle diameter of silica is 1 μm or less.

Second, the semiconductor device of the present invention is characterized in that a gap between the semiconductor chip and the wiring substrate is sealed using the first sealing liquid epoxy resin composition.

  According to the first aspect of the invention, a specific amount of a solid epoxy resin having high compatibility with the liquid epoxy resin is blended, and an inorganic filler having an average particle diameter of 1 μm or less is used, thereby being compatible with the liquid epoxy resin. The cured solid epoxy resin is dispersed in the cured product as a fine resin portion after curing, and functions as a stress relaxation material. Therefore, it is possible to reduce the stress without affecting other physical properties such as an underfill material, thereby improving the reliability of the package.

  In addition, the stress relaxation by a solid epoxy resin expresses effectively by using the inorganic filler which has the above average particle diameters. In other words, cracks that cause stress on the resin (cracks on the resin) are generally considered to occur at the interface between the inorganic filler and the resin. When the average particle size of the inorganic filler is large, cracks grow macroscopically between the inorganic fillers. However, it is considered that the solid epoxy resin, which is a low stress component, does not work as a stress relaxation material.

  On the other hand, when the average particle size of the inorganic filler is small, the low stress component that exists macroscopically becomes more dominant than the microscopically existing inorganic filler interface. It is thought to be effectively expressed.

According to the second aspect, since the semiconductor element is sealed using the liquid epoxy resin composition for sealing according to the first aspect, the stress of the sealing resin is relieved and the semiconductor has high reliability. It can be a device.

  Hereinafter, the present invention will be described in detail.

  The epoxy resin that is liquid at room temperature used in the present invention has two or more functional epoxy groups in one molecule. Specific examples thereof include bisphenols such as bisphenol A type epoxy resin and bisphenol F type epoxy resin. Cresol novolac epoxy resins such as epoxy resin and O-cresol novolac epoxy resin. These may be used alone or in combination of two or more. Here, “normal temperature” means 25 ° C.

  The epoxy resin solid at room temperature used in the present invention has two or more functional epoxy groups in one molecule. Specific examples thereof include a cresol novolac type epoxy resin, a phenol novolac type epoxy resin, and a cresol. Examples thereof include naphthol type epoxy resins, biphenyl type epoxy resins, biphenyl aralkyl type epoxy resins, naphthalene skeleton type epoxy resins, dicyclopentadiene type epoxy resins, and bromine-containing epoxy resins. These may be used alone or in combination of two or more.

  Here, “normal temperature” has the same meaning as described above, and “solid” means a solid or semi-solid state having no fluidity. From the point of obtaining the effect of the present invention, the softening point of the epoxy resin solid at room temperature is preferably 60 ° C. or higher, more preferably 60 to 100 ° C. in terms of the softening point by the ring and ball method.

  The content of the epoxy resin that is solid at normal temperature is 15 to 50% by mass, more preferably 20 to 40% by mass, based on the total amount of the epoxy resin that is liquid at normal temperature and the epoxy resin that is solid at normal temperature. If the blending amount of the epoxy resin that is solid at room temperature is outside the range, the stress relaxation action cannot be sufficiently obtained.

  It is desirable that the epoxy resin solid at room temperature has a particle diameter larger than that of the inorganic filler and an occupied area larger than that of the inorganic filler from the viewpoint of effectively exerting the stress relaxation effect. The solid epoxy resin usually has a particle diameter of several μm or more.

  Specific examples of the curing agent used in the present invention include alicyclic acid anhydrides such as methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenone. And aromatic acid anhydrides such as tetracarboxylic acid. These may be used alone or in combination of two or more.

  In this invention, it is preferable to use an acid anhydride as a hardening | curing agent, and it is preferable that the ratio of the acid anhydride in a hardening | curing agent shall be 50 mass% or more. By using an acid anhydride as a curing agent, the effect of the present invention that achieves low stress using a liquid epoxy resin and a solid epoxy resin can be sufficiently exerted.

  That is, when an acid anhydride is used as a curing agent, the cured product tends to be hard and brittle, but this can be effectively compensated by the stress relaxation action of the solid epoxy resin.

  In addition to the above acid anhydrides, phenol novolak, cresol novolak, phenol aralkyl resin, naphthol aralkyl resin, dicyclopentadiene type, triphenylmethane type, zyloc type, terpene type, etc. May be.

  The amount of the curing agent is preferably such that the equivalent ratio of the curing agent equivalent to the epoxy equivalent of the epoxy resin (hardening agent equivalent / epoxy equivalent) is 0.5 to 1.5, more preferably equivalent. The amount is such that the ratio is 0.7 to 1.3. If the equivalent ratio is less than 0.5, the curing characteristics may be reduced, and if the equivalent ratio exceeds 1.5, the physical properties of the cured product may be reduced.

  Specific examples of the curing accelerator used in the present invention include 2-methylimidazole, 2-ethylimidazole, 1,2-dimethylimidazole, 1,2-diethylimidazole, 2-ethyl-4-methylimidazole, 2-un Imidyl compounds such as decylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, organic phosphines such as triphenylphosphine, tertiary amines such as 1,8-diazabicyclo (5,4,0) undecene, amines Examples thereof include adduct compounds. These may be used alone or in combination of two or more.

  As for the compounding quantity of a hardening accelerator, 0.1-5.0 mass% is preferable with respect to the total amount of liquid and solid epoxy resin, and a hardening | curing agent. When the blending amount of the curing accelerator is less than 0.1% by mass, the curing accelerating action may be insufficient, and when the blending amount of the curing accelerator exceeds 5.0% by mass, the curing characteristics are deteriorated. There is a case.

  Specific examples of the inorganic filler used in the present invention include fused silica, crystalline silica, finely divided silica, alumina, silicon nitride, magnesia and the like. These may be used alone or in combination of two or more.

  The average particle diameter of the inorganic filler is 1 μm or less, more preferably 0.3 to 1 μm. The average particle diameter can be measured by a laser diffraction / scattering method. Among inorganic fillers having such an average particle diameter, spherical fused silica is particularly preferable. In a material that requires fluidity, such as an underfill material, when crushed silica is used, resistance at the time of fluidization increases, but fluidity can be improved by using spherical fused silica.

  The blending amount of the inorganic filler is preferably 30 to 75% by mass, more preferably 40 to 70% by mass with respect to the total amount of the liquid epoxy resin composition for sealing. If the blending amount of the inorganic filler is less than 30% by mass, the coefficient of linear expansion becomes large, and there is a risk of causing the occurrence of cracks in the package thermal test. When the blending amount of the inorganic filler exceeds 75% by mass, the viscosity of the liquid epoxy resin composition for sealing becomes high, and when the gap between the semiconductor chip and the wiring board is filled as an underfill material, the penetration property into the gap is increased. May decrease.

  The liquid epoxy resin composition for sealing of the present invention can further contain other additives within a range not impairing the effects of the present invention. Specific examples of such additives include coupling agents such as γ-glycidoxypropyltrimethoxysilane and γ-mercaptopropyltrimethoxysilane, flame retardants, colorants, reactive diluents, modifiers, solvents Etc.

  The liquid epoxy resin composition for sealing according to the present invention may include, for example, the above liquid and solid epoxy resin, a curing agent, a curing accelerator, an inorganic filler, and other additives blended as necessary at the same time or Separately, it can be obtained by stirring, dissolving, mixing, dispersing, and vacuum degassing while applying heat treatment if necessary. As a device for mixing, stirring, dispersing and the like, for example, a disper, a planetary mixer, a three-roll, a ball mill, a laika machine equipped with a stirring and heating device, and the like can be used.

  The semiconductor device of the present invention can be manufactured by sealing between the semiconductor chip and the wiring board with the sealing liquid epoxy resin composition obtained as described above. For example, the liquid epoxy resin composition for sealing of the present invention is dispensed in the gap between bumps of a semiconductor chip such as an IC or LSI mounted on a wiring pattern surface of a wiring board of FR grade or the like via a plurality of bumps. After applying and filling with a semiconductor chip, etc., a flip-chip type semiconductor device can be manufactured through subsequent processes such as heat-curing and then sealing the entire semiconductor chip.

  In addition, although hardening conditions are not specifically limited, For example, they are 120-170 degreeC and 0.5 to 5 hours.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples at all. In addition, the compounding quantity shown in Table 1 represents a mass part.
[Examples 1 to 3 and Comparative Examples 1 to 7]
Prepared by mixing a liquid epoxy resin composition for sealing in which each component is blended in the blending amounts shown in Table 1 with a main agent containing an epoxy resin and a mixture containing a curing agent and a curing accelerator according to a conventional method. did.

As the blending components shown in Table 1, the following were used.
Liquid epoxy resin: bisphenol A type epoxy resin (Japan Epoxy Resin Co., Ltd. “Epicoat 828” viscosity of 1200 to 1500 mPa · s (25 ° C.) epoxy equivalent 189)
Solid epoxy resin (1): O-cresol novolac type epoxy resin (Sumitomo Chemical Co., Ltd. “ESCN195XL” epoxy equivalent 195)
Solid epoxy resin (2): biphenyl type epoxy resin (Japan Epoxy Resin Co., Ltd. “YX4000H” epoxy equivalent 187-197 melting point 105 ° C. (DSC method))
Low elastic modulus agent (1): Silicone oil (Toray Dow Corning Co., Ltd. “SF-8413”)
Low elastic modulus agent (2): Solid silicone powder (Toray Dow Corning “E500”)
Curing agent: Methylhexahydrophthalic anhydride (Hitachi Chemical Industry Co., Ltd. “HN-5500E”)
Curing accelerator: 2-ethyl-4-methylimidazole (Shikoku Kasei Kogyo Co., Ltd. “2E4MZ”)
Inorganic filler: Spherical fused silica (ADMATEX “SO-E2”, average particle size 0.5 μm)
Coupling agent: γ-glycidoxypropyltrimethoxysilane (Nihon Unicar Co., Ltd. “A187”)
[Compatibility evaluation]
The viscosity of the sealing liquid epoxy resin compositions of Examples and Comparative Examples was measured at 25 ° C., 5 rpm, and 50 rpm using a B8H type rotational viscometer. The compatibility was judged from the value of the thixo ratio (5 rpm viscosity / 50 rpm viscosity) of 5 rpm viscosity and 50 rpm viscosity. The greater the thixo ratio, the poorer the wettability of the solid resin with respect to the liquid resin, and the better the compatibility. Discrimination criteria were defined as follows.
○: Thixo ratio less than 1.5 ×: Thixo ratio 1.5 or more
[Reliability test]
Semiconductor device using liquid epoxy resin compositions for sealing of Examples and Comparative Examples applied on FR4 substrate, measuring warpage of substrate diagonal after curing, and using the composition as underfill based on the average value Judgment of reliability. It is considered that the smaller the warp, the better the stress relaxation and the lowering of the stress. Discrimination criteria were defined as follows.
○: Less than 10 mm ×: 10 mm or more Table 1 shows the results of the compatibility evaluation and the reliability test.

  As shown in Table 1, an epoxy resin that is liquid at normal temperature and a specific amount of epoxy resin that is solid at normal temperature with respect to the total amount of epoxy resin are blended, and furthermore, has a specific average particle size as an inorganic filler. In Examples 1 to 3 blended with spherical fused silica, the compatibility of the solid epoxy resin is good, the warpage of the cured product is small, and the stress is relaxed. By using this as an underfill material, etc. A highly reliable semiconductor device can be obtained.

  On the other hand, Comparative Example 1 in which the solid epoxy resin was not blended at room temperature, Comparative Example in which the solid epoxy resin was blended at room temperature, but the blending amount was excessive or too small relative to the total amount of the epoxy resin In Comparative Example 4 in which only a solid epoxy resin was blended at 2, 3 and room temperature and no liquid epoxy resin was blended at room temperature, a large warp occurred in the cured product.

  Further, in Comparative Examples 5 and 6 in which silicone oil was blended as a low elastic modulus agent without blending a solid epoxy resin at room temperature, and in Comparative Example 7 in which solid silicone powder was blended, curling of the cured product was suppressed. However, the compatibility was low.

Claims (2)

In a liquid epoxy resin composition for sealing for underfill (excluding the method of applying to a wafer on which a large number of semiconductor elements having solder bumps are formed to make a B-stage), a bisphenol A type liquid at room temperature Epoxy resin , O-cresol novolak type epoxy resin and biphenyl type epoxy resin selected from solid epoxy resin at normal temperature, acid anhydride curing agent, curing accelerator, and spherical fused silica as inorganic filler The sealing is characterized in that the content of the epoxy resin solid at normal temperature is 15 to 50% by mass with respect to the total amount of the epoxy resin, and the average particle diameter of the spherical fused silica is 1 μm or less. Liquid epoxy resin composition. A semiconductor device, wherein a space between a semiconductor chip and a wiring board is sealed using the liquid epoxy resin composition for sealing according to claim 1.