JP5201451B2 - Epoxy resin composition for semiconductor encapsulation - Google Patents

Description

  The present invention relates to an epoxy resin composition for semiconductor encapsulation, and in particular, to provide a sealed semiconductor device that includes a combination of a specific curing agent and a filler, has low warpage, and has excellent reflow resistance and the like. The present invention relates to an epoxy resin composition for semiconductor encapsulation. The present invention also relates to a semiconductor device which is sealed with the resin composition and has a small warp and is suitable for surface mounting.

  Conventionally, resin-sealed diodes, transistors, ICs, LSIs, and super LSIs have been the mainstream of semiconductor devices. An epoxy resin composition is generally used for resin sealing because it is excellent in moldability, adhesiveness, electrical properties, mechanical properties, moisture resistance, and the like. However, with the high integration of semiconductor elements, the progress of surface mounting technology and the use of lead-free solder in the past few years, further improvements are required in the above characteristics.

  For example, a plurality of semiconductor elements such as a ball grid array (BGA) and a MAP (multi-array package) such as QFN, which have become mainstream in recent years, are mounted on a substrate, and each semiconductor element is sealed after resin sealing. Since the CSP (chip size package) to be singulated is large, the filling property of the sealing resin, that is, the ability of the resin to wrap around every corner to form a cured product without defects, Warping after molding due to sealing only has become a big problem.

The volume of sealing resin occupies less of the total package volume, especially as the size of chips increases due to high integration, the density of semiconductor elements increases for cost reduction, the MAP sealing area increases, and the package becomes thinner. It has become. In these semiconductor devices, contrary to the conventional devices, when the semiconductor element mounting side is turned up, the warp tends to be convex. In order to prevent such convex warpage, it is conceivable to reduce the amount of the inorganic filler. However, if the amount of the filler is small, the moisture absorption of the cured resin increases, and cracks due to thermal shock during the reflow process and peeling from the substrate or semiconductor element interface are likely to occur.

Another method is to use a filler having a relatively large thermal expansion. A composition using spherical cristobalite as such a filler has also been proposed (Patent Document 1). However, cristobalite undergoes a phase transition from α-cristobalite to β-cristobalite at 268 ° C., and the thermal expansion changes. Therefore, in the reflow process in which the maximum temperature is about 265 ° C., peeling may occur at the interface between the substrate and the cured encapsulated resin, or the warpage of the substrate may increase.
JP-A-11-302506

The present inventors have repeated research to provide an epoxy resin composition for semiconductor encapsulation, which can produce a sealed semiconductor device (hereinafter referred to as “sealing body”) with less warpage and without defects, It has been found that warpage can be reduced by a combination of a specific resin system and an inorganic filler (Japanese Patent Application No. 2007-049649). An object of this invention is to provide the composition for sealing which can reduce curvature further.

  As a result of intensive studies to achieve the above object, the present inventors have found that when a specific curing agent is used, a combination of inorganic fillers can achieve the above object.

（ｍは０〜１００の整数であり、Ｒ^１〜Ｒ^４は、互いに独立に、水素原子、炭素数１〜６のアルキル基又はアリール基である）
（Ｃ）球状溶融シリカを、組成物総質量の８２〜８７質量％となる量
（Ｄ）下記（２）式で表される硬化促進剤（ｄ１）及び（３）式で表される硬化促進剤（ｄ２）を、合計で成分（Ａ）と成分（Ｂ）の合計１００質量部に対して０．２〜３質量部となる量、且つ、（ｄ１）に対する（ｄ２）の質量比が０．３〜３となる量

（Ｒ^３は、互いに独立に、水素原子または炭素数１〜４のアルキル基、又はアルコキシ基である）

（Ｒ^４は、互いに独立に、水素原子、炭素数１〜４のアルキル基、アルコキシ基、又はヒドロキシ基である）。 That is, this invention is an epoxy resin composition for semiconductor sealing containing the following (A)-(D).
(A) Cresol novolak epoxy resin (B) A curing agent consisting only of a phenol aralkyl type resin represented by the following formula (1) is contained in the curing agent with respect to 1 mol of an epoxy group contained in the composition. Amount in which the molar ratio of phenolic hydroxyl group is 0.8 to 1.2

(M is an integer of 0 to 100, and R ^{1 to} R ⁴ are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group)
(C) Spherical fused silica in an amount of 82 to 87% by mass of the total mass of the composition (D) Curing accelerators represented by the following formula (2) (d1) and curing acceleration represented by formula (3) The amount of the agent (d2) is 0.2 to 3 parts by mass with respect to the total of 100 parts by mass of the component (A) and the component (B), and the mass ratio of (d2) to (d1) is 0. .3 to 3

(R ³ is, independently of each other, a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group)

^{(R 4} are, independently of one another, a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group, or hydroxy group).

  The composition of the present invention provides a sealed body with significantly small warpage and excellent reflow resistance.

Hereinafter, each component will be described in detail.
[(A) Cresol novolac epoxy resin]
The epoxy resin which is the main component of the composition of the present invention is a cresol novolac type epoxy resin (hereinafter referred to as “epoxy resin (A)”) represented by the following formula (4) in terms of moldability and thermal expansion / shrinkage. .

In Formula (4), n is 0-100, The average is 0.1-50, Preferably it is 0.5-20. More preferably, n is 1 to 5, or a polystyrene equivalent weight average molecular weight is 300 to 1500. Further, in accordance with ASTM D4287, the ICI viscosity measured at 150 ° C. using a cone / plate viscometer is 0.1 Pa · s or less, and a large amount of (C) spherical inorganic filler described later is blended. Is preferable, and more preferably 0.01 to 0.1 Pa · s.

In addition to the epoxy resin (A), another epoxy resin may be used in combination in such an amount that the object of the present invention is not impaired. Other epoxy resins include, for example, triphenolalkane type epoxy resins, aralkyl type epoxy resins, biphenyl skeleton-containing aralkyl type epoxy resins, biphenyl type epoxy resins, dicyclopentadiene type epoxy resins, heterocyclic type epoxy resins, and naphthalene rings. An epoxy resin, a bisphenol A type epoxy compound, a bisphenol F type epoxy compound, a bisphenol S type epoxy compound, a stilbene type epoxy resin and the like can be mentioned, and these two or more types can be used in combination.

It is preferable that the epoxy resin (A) has a hydrolyzable chlorine of 1000 ppm or less, particularly 500 ppm or less, and the amount of sodium and potassium is 10 ppm or less, respectively. A semiconductor device encapsulated with a resin having a hydrolyzable chlorine content exceeding 1000 ppm or a sodium or potassium content exceeding 10 ppm tends to deteriorate its moisture resistance even when left for a long time under high temperature and high humidity. .

式（１）において、ｍは０〜１００の整数であり、好ましくは、１〜１０である。Ｒ¹〜Ｒ⁴は、互いに独立に、水素原子、炭素数１〜6のアルキル基又はアリール基であり、好ましくは水素原子及びメチル基である。 [(B) phenol aralkyl type curing agent]
The curing agent (B) used in the present invention is represented by the following formula (1).

In Formula (1), m is an integer of 0-100, Preferably it is 1-10. R ^{1 to} R ⁴ are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an aryl group, preferably a hydrogen atom and a methyl group.

The cured product of the phenol aralkyl type curing agent and the epoxy resin (A) has a large amount of thermal expansion and thermal shrinkage, and is effective for reducing the warpage of the semiconductor element in which the volume ratio of the semiconductor element occupies the encapsulant volume is high. It is. The content of the curing agent in the composition is such that the molar ratio of the phenolic hydroxyl group contained in the curing agent is 0.8 to 1.2 with respect to 1 mole of the epoxy group contained in the composition. is there. When the ratio is outside the above range, the warping of the sealing body is large and the reflow resistance tends to be inferior.

  Similarly to the epoxy resin (A), the curing agent (B) preferably has an amount of sodium and potassium of 10 ppm or less. In a sealed body using a curing agent in which sodium or potassium exceeds 10 ppm, moisture resistance may deteriorate when the semiconductor device is left under high temperature and high humidity for a long time.

[(C) Spherical fused silica]
In the composition of the present invention, the amount of (C) spherical fused silica is 82 to 87% by weight of the total weight of the composition. If it is less than the said lower limit, the moisture absorption amount of hardened | cured material may become large and a reflow-proof characteristic may fall. When the upper limit is exceeded, the melt viscosity of the composition increases, wire flow occurs, defects occur in the cured product, and convex warpage may increase.

The average particle size (d ₅₀ ) of the spherical fused silica is preferably 5 to 40 μm, more preferably 7 to 30 μm. The average particle diameter can be measured by, for example, a laser diffraction / scattering method.

  The spherical filler is preferably surface-treated in advance with a coupling agent such as a silane coupling agent or a titanate coupling agent in order to increase the bond strength with the resin component. As such a coupling agent, epoxy silane such as γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, N -Β (aminoethyl) -γ-aminopropyltrimethoxysilane, reaction product of imidazole and γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, etc. It is preferable to use a silane coupling agent such as mercaptosilane such as aminosilane, γ-mercaptosilane, and γ-episulfideoxypropyltrimethoxysilane. The blending amount of the coupling agent and the surface treatment method may be in accordance with conventional methods.

Ｒ^３は、互いに独立に、水素原子または炭素数１〜４のアルキル基、又はアルコキシ基であり、好ましくは水素原子である。

Ｒ^４は、互いに独立に、水素原子、炭素数１〜４のアルキル基、アルコキシ基、又はヒドロキシ基であり、好ましくは水素原子である。 [(D) Curing accelerator]
In order to accelerate the reaction between the epoxy resin (A) and the curing agent (B), the composition of the present invention is represented by the curing accelerators (d1) and (4) represented by the following formula (3). A curing accelerator (d2) is included.

R ³ is independently of each other a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group, preferably a hydrogen atom.

R ⁴ is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group, or a hydroxy group, preferably a hydrogen atom.

As for content in the composition of a hardening accelerator (D), the total mass of (d1) and (d2) is 0.2-3 mass with respect to a total of 100 mass parts of a component (A) and a component (B). Part, preferably 0.9 to 2 parts by weight. If the content is less than the lower limit, the time until curing becomes too long, and the productivity is lowered. When it is larger than the upper limit, the curing time is shortened, which tends to cause unfilling, wire flow, and the like.

  Further, the mass ratio of (d2) to (d1), (d2) / (d1), is 0.3 to 3, preferably 0.5 to 3. Even if the total mass of (d1) and (d2) is the same, if the mass ratio is less than the lower limit value, the curability may be accelerated and the filling property may be insufficient. Insufficient properties may cause warping and reflow resistance may decrease. (D1) and (d2) may be blended as they are or after being premixed with the curing agent (B).

  In addition to the above components, various additives can be blended in the resin composition of the present invention as necessary. For example, release agents such as carnauba wax and fatty acid esters, colorants such as carbon black, zinc molybdate-supported talc, zinc molybdate-supported zinc, phosphazene compounds, flame retardants such as silicone compounds, hydrotalcites, bismuth compounds, Examples include halogen trapping agents such as rare earth oxides.

[Preparation of epoxy resin composition, etc.]
In the sealing resin composition of the present invention, the components (A) to (D) and, if desired, the above additives are blended at a predetermined composition ratio, and this is mixed thoroughly by a mixer or the like to make it uniform. It can be prepared by carrying out a melt mixing process using a roll, a kneader, an extruder, etc., then cooling and solidifying, and then pulverizing to an appropriate size.

  In addition, when mixing a composition with a mixer etc., you may mix | blend a silane coupling agent as a wetter. As the silane coupling agent, those already described with respect to the surface treatment of the spherical filler can be used.

Thus obtained resin composition for encapsulating a semiconductor of the present invention can be effectively used for encapsulating various semiconductor devices. The most common method for sealing is a low-pressure transfer molding method, and the molding temperature is 150 to 185 ° C. and 30 to 180 seconds. Further, it is desirable to perform post-curing at 150 to 185 ° C. for 2 to 20 hours.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, this invention is not restrict | limited to the following Example.

[Examples 1-5, Comparative Examples 1-5]
Each component (parts by mass) shown in Table 2 was uniformly melt-mixed with two hot rolls, cooled, then pulverized to obtain an epoxy resin composition for semiconductor encapsulation. Each component in the table is shown below.

（Ｍｗ＝５００）
（Ｂ）フェノールアラルキル硬化剤
（ロ）下記式（1）式で表されるフェノールアラルキル樹脂

（式中 Ｒ^１及びＲ^３は水素、Ｒ^２及びＲ^４はメチル基、Mｗ＝１，３００）
（Ｃ）球状充填剤
（ホ）球状溶融シリカ：平均粒径１２μｍ（（株）龍森製）
（Ｄ）硬化促進剤
（ト）硬化促進剤（ｄ１）

（チ）硬化促進剤（ｄ２）：ＴＰＰ−Ｋ（北興化学（株）製）

その他の成分
（リ）離型剤：カルナバワックス、TOWAX132（東亜化成株式会社製）
（ヌ）シランカップリング剤：ＫＢＭ−４０３、γ−グリシドキシプロピルトリメトキシシラン（信越化学工業（株）製）
（ル）着色剤：デンカブラック（電気化学工業（株）製）
比較例で使用の材料
（Ｂ）以外の硬化剤
（ハ）ＭＥＨ−７８００ＳＳ（明和化成（株）製）フェノール性水酸基当量１７５）

（Ｍｗ＝９００）
（ニ）ＭＥＨ−７８５１ＳＳ（明和化成（株）製）フェノール性水酸基当量１９９

（Ｍｗ＝７６０）
（ヘ）球状クリストバライト： 粒径２６μｍ（（株）龍森製） (A) Cresol novolac epoxy resin (A) Cresol novolac epoxy resin of formula (4): EOCN-1020-55, manufactured by Nippon Kayaku Co., Ltd.)

(Mw = 500)
(B) Phenol aralkyl curing agent (b) Phenol aralkyl resin represented by the following formula (1)

(Wherein R ¹ and R ³ are hydrogen, R ² and R ⁴ are methyl groups, Mw = 1,300)
(C) Spherical filler (e) Spherical fused silica: average particle size 12 μm (manufactured by Tatsumori)
(D) Curing accelerator (G) Curing accelerator (d1)

(H) Curing accelerator (d2): TPP-K (manufactured by Hokuko Chemical Co., Ltd.)

Other ingredients (Li) Release agent: Carnauba wax, TOWAX132 (manufactured by Toa Kasei Co., Ltd.)
(Nu) Silane coupling agent: KBM-403, γ-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.)
(L) Colorant: Denka Black (manufactured by Denki Kagaku Kogyo Co., Ltd.)
Curing agent other than the material (B) used in the comparative example (c) MEH-7800SS (manufactured by Meiwa Kasei Co., Ltd.) phenolic hydroxyl group equivalent 175)

(Mw = 900)
(D) MEH-7851SS (Maywa Kasei Co., Ltd.) phenolic hydroxyl group equivalent 199

(Mw = 760)
(F) Spherical cristobalite: particle size 26 μm (manufactured by Tatsumori)

The obtained composition was evaluated by the following methods. The results are shown in Table 2.
(A) Spiral flow value Using a mold conforming to the EMMI standard, measurement was performed under the conditions of 175 ° C. and 6.9 N / mm ² . 50 inches or more are preferable.
(B) Melt viscosity Using a Koka flow tester, the viscosity was measured at a temperature of 175 ° C. using a nozzle having a diameter of 1 mm under a pressure of 10 kgf. The minimum viscosity is preferably 10 Pa · s or less.
(C) Warpage amount A semiconductor device having the cross-sectional structure shown in FIG. 1 but the number of chips N shown in Table 1 (device 1: 4 × 4, device 2: 5 × 5) was manufactured. The sizes F to L in Table 1 are as shown in FIG. The used substrates and die bonding agents are as follows.
Organic circuit board: CCL-HL-832, manufactured by Mitsubishi Gas Chemical Co., Ltd., glass transition temperature 180 ° C., coefficient of thermal expansion below glass transition temperature 1.5 × 10 ⁻⁵ / ° C., coefficient of thermal expansion / shrinkage above glass transition temperature 1 × 10 ⁻⁵ / ° C .;
Die-bonding agent: Able 6202C, manufactured by Japan Ablestick, glass transition temperature 40 ° C., thermal expansion below glass transition temperature 7.0 × 10 ⁻⁵ / ° C., coefficient of thermal expansion above glass transition temperature 35.0 × 10 ⁻⁵ / ° C. The thickness after curing is 50 μm.
The above device was sealed with each composition at 175 ° C., 6.9 N / mm ² and a molding time of 120 seconds. After cooling the obtained semiconductor device to room temperature, the height displacement was measured in a diagonal direction using a laser three-dimensional measuring machine, and the largest value of the displacement difference was taken as the amount of warpage of the substrate. In Table 3, the value of the convex warp is represented by a positive value, and the value of the concave warp is represented by a negative value. It is preferably +/− 500 μm or less.

（ｄ）耐リフロー性
反り量の測定をした半導体装置２を、チップ毎に切断し、８５℃／６０％ＲＨの恒温恒湿器に１６８時間放置した後、半導体パッケージの表面温度が、図３に示す変化を示すような温度プロフィールのＩＲリフローを３回通した後に、超音波探査装置を用いて内部クラック又は剥離の発生したチップ数を数えた。

(D) The semiconductor device 2 whose reflow resistance warpage amount was measured was cut for each chip and left in a constant temperature and humidity chamber of 85 ° C./60% RH for 168 hours. After passing IR reflow of the temperature profile which shows the change shown in 3 times, the number of chips having internal cracks or peeling was counted using an ultrasonic probe.

The devices sealed with the compositions of Examples 1 to 5 all had a warp of 500 μm or less, and were excellent in reflow resistance.
On the other hand, the device sealed with the composition of Comparative Examples 1 and 2 containing a curing agent other than the component (B) of the present invention, particularly the device 2, was greatly warped.
The composition of Comparative Example 3 with a small amount of spherical silica was warped in apparatus 1, and the composition of Comparative Example 4 with a large amount of spherical silica was warped in apparatus 2, respectively.
The composition of Comparative Example 5 contained spherical cristobalite, and the device sealed with the composition was cracked during the reflow process.

FIG. 6 is a cross-sectional view of an example of a board on chip ball grid array package. It is the top view and sectional drawing which show how to obtain | require the board | substrate on-chip ball grid array package created in the Example, and the volume of the semiconductor element in this package. It is a figure which shows the temperature profile of IR reflow used in the Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Epoxy resin composition 2 Semiconductor chip 3 Die bond layer 4 Organic circuit board 5 Wire 6 Epoxy resin composition

Claims (5)

An epoxy resin composition for semiconductor encapsulation containing the following (A) to (D) (A) a cresol novolac epoxy resin (B) a curing agent consisting only of a phenol aralkyl type resin represented by the following formula (1): The amount by which the molar ratio of the phenolic hydroxyl group contained in the curing agent is 0.8 to 1.2 with respect to 1 mol of the epoxy group contained in

(M is an integer of 0 to 100, and R ^{1 to} R ⁴ are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group)
(C) Spherical fused silica in an amount of 82 to 87% by mass of the total mass of the composition (D) Curing accelerators represented by the following formula (2) (d1) and curing acceleration represented by formula (3) The amount of the agent (d2) is 0.2 to 3 parts by mass with respect to the total of 100 parts by mass of the component (A) and the component (B), and the mass ratio of (d2) to (d1) is 0. .3 to 3

(R ³ is, independently of each other, a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group)

^{(R 4} are, independently of one another, a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group, or hydroxy group). (C) The composition of claim 1, wherein an average particle diameter of the spherical fused silica _{(d 50)} is 5 to 40 m. A semiconductor device sealed with a cured product of the epoxy resin composition according to claim 1. The semiconductor device according to claim 3, wherein a volume occupied by the semiconductor element is 21 to 32 % of the total volume of the semiconductor device. The semiconductor device according to claim 3, wherein the semiconductor device is surface-mounted on a substrate.

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