JP2000034393A - Epoxy resin composition for semiconductor encapsulation and semiconductor device - Google Patents

Abstract

(57) Abstract: (A) an epoxy resin represented by the general formula (1); (B) a phenol resin curing agent represented by the general formula (2); (C) a molybdenum compound; An epoxy resin composition for encapsulating a semiconductor, comprising an inorganic filler. Embedded image Embedded image (R ¹ and R ² are the same or different atoms or groups selected from H, a C ₁ -C ₄ alkyl group and a phenyl group,
n and m = 0 to 10. The epoxy resin composition for semiconductor encapsulation of the present invention provides a cured product excellent in moldability, flame retardancy, reflow crack resistance and moisture resistance, and further comprises a halogenated epoxy resin and antimony trioxide as a resin. Since it is not contained in the composition, there is no adverse effect on the human body and environment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a mold having good moldability,
The present invention relates to an epoxy resin composition for semiconductor encapsulation which has excellent high-temperature storage characteristics, flame retardancy and reflow crack resistance, and gives a highly safe cured product, and a semiconductor device sealed with a cured product of the resin composition.

[0002]

2. Description of the Related Art
As semiconductor devices, resin-sealed diodes, transistors, ICs, LSIs, and super LSIs have become mainstream,
In general, epoxy resin is more moldable than other thermosetting resins,
Semiconductor devices are often sealed with epoxy resin compositions because of their excellent adhesiveness, electrical properties, mechanical properties, moisture resistance, and the like.

In recent years, in order to achieve V-0 of UL-94, which is a flame retardant standard, this epoxy resin composition has
Generally, a halogenated epoxy resin and antimony trioxide are blended. The combination of the halogenated epoxy resin and antimony trioxide has a large radical trapping and air blocking effect in the gas phase, and as a result, a high flame retardant effect can be obtained.

[0004] However, halogenated epoxy resins have the problem of generating toxic gases when burned.
Since antimony trioxide also has powder toxicity, considering the effects on human body and environment, these flame retardants are hardly suitable as a resin composition component, and it is desirable not to include them at all.

To meet such demands, hydroxides such as Al (OH) ₃ and Mg (OH) ₂ , phosphorus-based flame retardants and the like have conventionally been used in place of halogenated epoxy resins or antimony trioxide. Consideration has been given to its use. However, any of these compounds has problems such as poor curability during molding and poor moisture resistance, and has not been put to practical use at present.

The present invention has been made in view of the above circumstances,
Provided is an epoxy resin composition for semiconductor encapsulation which is excellent in moldability, excellent in high-temperature storage characteristics, flame retardancy and reflow crack resistance and gives a highly safe cured product, and a semiconductor device sealed with the cured product. The purpose is to do.

[0007]

Means for Solving the Problems and Embodiments of the Invention The present inventors have made intensive studies to achieve the above object, and as a result, as an epoxy resin, an epoxy resin represented by the following general formula (1): By mixing a molybdenum compound as a flame retardant with an epoxy resin composition for semiconductor encapsulation containing a phenol resin represented by the following general formula (2) as a curing agent and an inorganic filler as essential components, It has moldability, is excellent in flame retardancy, reflow crack resistance and moisture resistance, and obtains a cured product with high safety, and found that a semiconductor device sealed with this cured product has high reliability. Was.

In this case, molybdenum compounds such as zinc molybdate are known to be effective in reducing smoke and char formation during plastic combustion, and have been conventionally used in combination with a halogenated resin like antimony trioxide. Was. By mixing this molybdenum compound with the epoxy resin of the formula (1) and the phenol resin of the formula (2), which are heat-resistant resins, sufficient flame retardancy can be obtained without using a halogenated resin. The molybdenum compound can be obtained, and the molybdenum compound does not exhibit powder toxicity like antimony trioxide, and does not reduce the curability and moisture resistance. The inventors have found that they can be blended, and have accomplished the present invention.

[0009]

Embedded image (Wherein, R ¹ is the same or different atom or group selected from a hydrogen atom, an alkyl group having 1 to 4 carbon atoms and a phenyl group, and n is an integer of 0 to 10.)

[0010]

Embedded image (Wherein, R ² is the same or different atom or group selected from a hydrogen atom, an alkyl group having 1 to 4 carbon atoms and a phenyl group, and m is an integer of 0 to 10). Is composed of (A) an epoxy resin represented by the general formula (1), (B) a phenolic resin curing agent represented by the general formula (2), (C) a molybdenum compound, and (D) an inorganic filler. An epoxy resin composition for semiconductor encapsulation, and a semiconductor device encapsulated with the epoxy resin composition for semiconductor encapsulation.

Hereinafter, the present invention will be described in more detail. In the epoxy resin composition for semiconductor encapsulation of the present invention, the epoxy resin represented by the following general formula (1) of the component (A) and the epoxy resin of the component (B) The phenol resin curing agent represented by the general formula (2) is a resin having a biphenyl skeleton and a phenol skeleton. These resins have low water absorption and excellent toughness, give a cured product exhibiting excellent reflow crack resistance, and have a high thermal decomposition initiation temperature,
Due to its low thermal decomposition rate, it is a material with excellent heat resistance.

The component (A) is a phenol aralkyl type epoxy resin having a biphenyl skeleton represented by the following general formula (1) (that is, an epoxy resin having a biphenyl aralkyl skeleton). And the like.

[0013]

Embedded image (Where R ¹ is a hydrogen atom, a methyl group, an ethyl group, n
-Propyl group, isopropyl group, n-butyl group, isobutyl group, the same or different atoms or groups selected from phenyl group such as an alkyl group having 1 to 4 carbon atoms such as tert-butyl group, n is 0-10, Preferably 0
4, more preferably an integer of 0 to 2. )

[0014]

Embedded image (N is 0-10, preferably 0-4, more preferably 0
整数 2. )

The epoxy resin represented by the above formula (1)
A resin melt viscosity measured by an ICI viscometer (cone plate type) at 150 ° C. of 0.1 to 2.5 poise;
In particular, it is preferably 0.1 to 0.8 poise. When the resin melt viscosity exceeds 2.5 poise, when the amount of the inorganic filler is as high as 80 to 90% by weight for improving the reflow crack resistance, the fluidity during melting may be significantly reduced. If it is less than 0.1 poise, internal voids are likely to occur during molding, and the reliability may decrease.

In the present invention, another epoxy resin can be used in combination as needed. Other epoxy resins used in combination include novolak epoxy resins such as phenol novolak epoxy resins and cresol novolak epoxy resins, triphenolalkane epoxy resins such as triphenolmethane epoxy resins and triphenolpropane epoxy resins, and biphenyls. Epoxy resin, phenol aralkyl epoxy resin containing no biphenyl skeleton, heterocyclic epoxy resin, naphthalene ring-containing epoxy resin, bisphenol A
Type epoxy resin, bisphenol type epoxy resin such as bisphenol F type epoxy resin, stilbene type epoxy resin, etc., and one or more of these can be used. Among these, a biphenyl type epoxy resin, a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, a stilbene type epoxy resin and the like which have a low viscosity when melted are preferred.

The amount of the epoxy resin represented by the formula (1) is 50 to 100% by weight based on the total amount of the epoxy resin (the epoxy resin represented by the formula (1) + another epoxy resin).
In particular, the content is desirably 70 to 100% by weight. If the amount of the epoxy resin of the formula (1) is less than 50% by weight,
Sufficient reflow crack resistance and flame retardancy may not be obtained.

The component (B) is a aralkyl-type phenol resin having a biphenyl skeleton (that is, a phenol resin having a biphenyl aralkyl skeleton) represented by the following general formula (2). The following can be mentioned.

[0019]

Embedded image (Where R ² is a hydrogen atom, a methyl group, an ethyl group, n
-Propyl group, isopropyl group, n-butyl group, isobutyl group, the same or different atoms or groups selected from a phenyl group such as an alkyl group having 1 to 4 carbon atoms such as tert-butyl group, m is 0-10, Preferably 0
4, more preferably an integer of 0 to 2. )

[0020]

Embedded image (M is 0-10, preferably 0-4, more preferably 0
整数 2. )

The phenolic resin curing agent represented by the formula (2) of the component (B) used in the present invention has an IC at 150 ° C.
It is desirable that the resin melt viscosity measured by an I viscometer (cone plate type) is 0.1 to 1.2 poise, particularly 0.2 to 0.8 poise. This is for the same reason as the epoxy resin.

In the present invention, if necessary, another curing agent can be used in combination as a curing agent. As other curing agents to be used in combination, for example, phenol novolak resin, novolak type phenol resin such as cresol novolak resin,
Naphthalene ring-containing phenolic resin, phenol aralkyl type phenolic resin containing no biphenyl skeleton, biphenyl type phenolic resin, triphenolmethane type phenolic resin, triphenolalkane type phenolic resin such as triphenolpropane type phenolic resin, alicyclic phenolic resin, Bisphenol type phenol resins such as a heterocyclic type phenol resin, a bisphenol A type phenol resin, a bisphenol F type phenol resin and the like can be mentioned, and one or more of these can be used.

The blending amount of the phenolic resin curing agent represented by the formula (2) is 50 to the total amount of the phenolic resin curing agent (the phenolic resin curing agent represented by the formula (2) + the other phenolic resin curing agent). It is desirable that the content be from 100 to 100% by weight, especially from 70 to 100% by weight. If the blending amount of the phenol resin curing agent of the formula (2) is less than 50% by weight, sufficient reflow crack resistance and flame retardancy may not be obtained.

In the present invention, the amount of the epoxy resin (A) and the amount of the curing agent (B) are not particularly limited, but are based on 1 mol of epoxy group contained in the total amount of epoxy resin in the composition. The molar ratio of the phenolic hydroxyl group contained in the total amount of the phenolic resin curing agent in the composition is 0.1.
A range of 5 to 1.5, particularly 0.8 to 1.2 is preferable.

The epoxy resin composition for semiconductor encapsulation of the present invention contains a molybdenum compound (C) as a flame retardant.

As the molybdenum compound of the component (C), molybdenum boride, molybdenum disilicide, molybdenum acetylacetonate, molybdenum oxide (IV), molybdenum oxide (V), molybdenum oxide (VI), zinc molybdate, Examples include molybdenum oxides, molybdenum borides, molybdenum silicides, molybdenum ester compounds, molybdates, and the like, such as calcium molybdate carbonate and calcium molybdate. The molybdenum compound is known to have a smoke reducing effect and an action of promoting formation of a carbonized layer at the time of plastic combustion, and conventionally, like antimony trioxide, was used in combination with a halogenated resin. By using in combination with the epoxy resin (A) having the specific structure and the phenol resin curing agent (B) having the specific structure, the V-form of UL-94 can be obtained without adding antimony trioxide or a halogenated resin. It has been found that excellent flame retardancy achieving −0 can be obtained. The molybdenum compound is an extremely safe flame retardant because it does not have powder toxicity like antimony trioxide and does not generate harmful gas due to thermal decomposition unlike halogenated resins. Among them, zinc molybdate is particularly preferred as a compound that does not adversely affect the curability of the epoxy resin composition.

The molybdenum compound may be blended as it is, but is preferably dispersed uniformly in the epoxy resin composition in order to obtain a sufficient flame retardant effect. It is desirable that a molybdenum compound such as zinc molybdate be supported on a fine inorganic filler (powder) such as talc or spherical fused silica and then blended as a molybdenum compound-supported inorganic filler. In this case, examples of the inorganic filler include silica such as fused silica and crystalline silica, talc, alumina, silicon nitride, aluminum nitride, boron nitride, titanium oxide, and glass fiber. Particularly, talc and spherical fused silica are preferable from the viewpoint of dispersibility in the epoxy resin composition.

Preferably, the molybdenum compound such as zinc molybdate is added to the inorganic filler so that the content of the molybdenum compound is in the range of 1 to 50% by weight, especially 5 to 40% by weight, based on the total amount of the inorganic filler carrying the molybdenum compound. It is preferable that the composition is supported on a filler (powder). If the content is less than 1% by weight, sufficient flame retardancy may not be obtained. If the content is more than 50% by weight, the curability and moldability (or fluidity) of the composition may be obtained. May decrease.

The average particle size of the molybdenum compound and the inorganic filler carrying the molybdenum compound is 0.1 to 20 μm, particularly 0.2 to 10 μm, particularly 0.5 to 3 μm, and the BET
The specific surface area by the adsorption method is preferably 0.5 to 50 m ² / g, particularly preferably 0.7 to ²⁰ m ² / g. If the average particle size is too small or the specific surface area is too large, the dispersibility in the resin composition may be deteriorated. On the other hand, if the average particle size is too large or the specific surface area is too small, zinc molybdate may be used. It is difficult to uniformly support a molybdenum compound such as above on the above-mentioned inorganic filler, and the flame retardancy may decrease.

The average particle diameter can be determined as a weight average value (median diameter) using a particle size distribution measuring device such as a laser beam diffraction method.

As such an inorganic filler carrying zinc molybdate, a commercially available product can be used. For example, SHE
KWINGARD 12 from RWIN-WILLIAMS
K such as 60, 1261, 1270, 1271, 911C
EMGARD series and the like.

The compounding amount of the molybdenum compound is 0.1 to 30 parts by weight, preferably 0.15 to 10 parts by weight, especially 0.2 to 10 parts by weight based on 100 parts by weight of the total of the epoxy resin and the curing agent.
When the amount is less than 0.1 part by weight, a sufficient flame retardant effect may not be obtained, and when the amount exceeds 30 parts by weight, the curability may decrease. The compounding amount of the inorganic filler as a whole supporting a molybdenum compound such as zinc molybdate is 0.5 to 120 parts by weight, especially 1 to 100 parts by weight of the total of the epoxy resin and the phenol resin curing agent.
-80 parts by weight, particularly preferably 1-50 parts by weight.

As the inorganic filler of the component (D) blended in the epoxy resin composition of the present invention, those usually blended in the epoxy resin composition can be used. Examples of the inorganic filler other than the molybdenum compound-supporting inorganic filler in the component (C) include silicas such as fused silica and crystalline silica, alumina, silicon nitride, aluminum nitride, boron nitride, titanium oxide, and glass fiber. And the like.

The average particle size and shape of these inorganic fillers are not particularly limited, but spherical fused silica having an average particle size of 1 to 40 μm, particularly 5 to 20 μm is particularly preferable from the viewpoint of moldability and fluidity.

In order to increase the bonding strength between the resin and the inorganic filler, the inorganic filler may be blended with one that has been previously surface-treated with a coupling agent such as a silane coupling agent or a titanate coupling agent. preferable. Examples of such a coupling agent include epoxy functional groups such as γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, and β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane. Alkoxysilane, N-β (aminoethyl)-
amino-functional alkoxysilanes such as γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, and mercapto-functional alkoxysilanes such as γ-mercaptopropyltrimethoxysilane It is preferable to use The amount of the coupling agent used for the surface treatment and the surface treatment method are not particularly limited.

The amount of the inorganic filler is preferably 400 to 1100 parts by weight, more preferably 600 to 900 parts by weight, based on 100 parts by weight of the total amount of the epoxy resin and the curing agent. The coefficient increases, the stress applied to the semiconductor element increases, which may lead to deterioration of element characteristics.In addition, the amount of resin with respect to the entire composition increases, so that the flame retardancy intended for the present invention cannot be obtained. There are cases. On the other hand, when it exceeds 1100 parts by weight, the viscosity at the time of molding becomes high, and the moldability may deteriorate. In addition, this inorganic filler is 75 to 92% by weight of the whole composition, especially 83 to 9%.
The content is preferably 0% by weight.

In the present invention, it is preferable to add a curing accelerator in order to accelerate the curing reaction between the epoxy resin and the curing agent. The curing accelerator is not particularly limited as long as it accelerates the curing reaction. For example, triphenylphosphine, tributylphosphine, tri (p-methylphenyl) phosphine, tri (nonylphenyl) phosphine, triphenylphosphine triphenyl Borane,
Organophosphorus compounds such as tetraphenylphosphonium / tetraphenylborate, triethylamine, benzyldimethylamine, α-methylbenzyldimethylamine,
1,8-diazabicyclo (5.4.0) undecene-7
Tertiary amine compounds such as 2-methylimidazole,
2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-ethylimidazole, 4-methylimidazole, 4-ethylimidazole, 2-phenyl-
4-hydroxymethylimidazole, 2-ethyl-4-
Imidazole compounds such as methylimidazole, 1-cyanoethyl-2-methylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, and 2-phenyl-4,5-dihydroxymethylimidazole can be used.

The epoxy resin composition for semiconductor encapsulation of the present invention may further contain various additives as necessary. As additives, for example, thermoplastic resins, thermoplastic elastomers, organic synthetic rubbers, low stress agents such as silicones, carnauba wax, higher fatty acids, waxes such as synthetic waxes, coloring agents such as carbon black, halogen trapping agents, etc. Is mentioned. In addition, the compounding amount of these additives can be a usual amount within a range that does not hinder the effects of the present invention.

The epoxy resin composition for semiconductor encapsulation of the present invention is prepared by blending an epoxy resin, a curing agent, an inorganic filler, and other additives at a predetermined composition ratio, and mixing them sufficiently by a mixer or the like. , A hot roll, a kneader, an extruder, or the like, and then the mixture is cooled and solidified, and pulverized to an appropriate size to obtain a molding material.

The thus obtained epoxy resin composition for encapsulating a semiconductor of the present invention can be effectively used for encapsulating various semiconductor devices. In this case, the most common method of encapsulation is as follows. A low pressure transfer molding method may be used. The molding temperature of the epoxy resin composition for semiconductor encapsulation of the present invention is 150 to 180 ° C. for 30 to 180 seconds, and the post-curing is 15 to 180 ° C.
It is desirable to carry out at 0 to 180 ° C. for 2 to 16 hours.

[0041]

The epoxy resin composition for semiconductor encapsulation of the present invention provides a cured product having excellent moldability, flame retardancy, reflow crack resistance and moisture resistance, and further comprises a halogenated epoxy resin and antimony trioxide. Since it is not contained in the resin composition, there is no adverse effect on the human body and environment. Therefore, a semiconductor device sealed with the composition of the present invention has high reliability.

[0042]

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples. In the following examples, all parts are parts by weight.

Examples 1 to 9, Comparative Examples 1 to 4 Tables 1 and 2
The components shown in (1) and (2) were uniformly melted and mixed by a hot roll, cooled and pulverized to obtain an epoxy resin composition for semiconductor encapsulation.

The raw materials used are shown below. Epoxy resin (a) Epoxy resin represented by the formula (1-1): NC30
00P (manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent 272, resin melt viscosity at 150 ° C. by ICI viscometer (cone plate type) 0.8 poise) (b) Biphenyl type epoxy resin: YX4000HK
(Epoxy equivalent 190, manufactured by Yuka Shell) (c) o-cresol novolak type epoxy resin: EO
CN1020-55 (Nippon Kayaku, epoxy equivalent 20
0) Curing agent (d) Phenolic resin represented by formula (2-1): MEH
7851L (manufactured by Meiwa Kasei, phenol equivalent 199, 15
Resin melt viscosity of 0.8 poise by ICI viscometer (cone plate type) at 0 ° C.) (e) Phenol aralkyl resin: MEH7800SS
(Phenol equivalent: 175, manufactured by Meiwa Kasei Co., Ltd.)-Inorganic filler Spherical fused silica (average particle size: 13 μm)-Hardening accelerator: triphenylphosphine
Specific surface area (BET method) 12 m ² / g (molybdenum compound content: 19% by weight)) Release agent: carnauba wax (manufactured by Nikko Fine Products Co., Ltd.) Silane coupling agent: γ-glycidoxypropyl Trimethoxysilane, KBM403 (Shin-Etsu Chemical Co., Ltd.)
Made)

[0045]

Embedded image

Various properties of these compositions were measured by the following methods. The results are also shown in Tables 1 and 2. << Spiral flow value >> Using a mold conforming to the EMMI standard, 175 ° C., 70 kgf / cm ² , molding time 12
It was measured under the condition of 0 seconds. << Molding Hardness >> 175 ° C, 7 according to JIS-K6911
10 × 4 × under conditions of 0 kgf / cm ² and molding time of 90 seconds
The hot hardness when a 100 mm rod was formed was measured with a Barcol hardness tester. << Reflow crack resistance test >> A flat package of 14 × 20 × 2.7 mm was molded. The product post-cured at 180 ° C. for 4 hours is left in a constant temperature / humidity chamber of 85 ° C./85% RH for 168 hours to absorb moisture, and then immersed in a solder bath at a temperature of 240 ° C. for 30 seconds to remove cracks outside the package. Observation was made to determine the crack generation rate. << Flame Retardancy >> A 1/16 inch thick plate was molded and examined for flame retardancy based on the UL-94 standard. << Moisture Resistance >> A silicon chip having a size of 6 × 6 mm on which aluminum wiring was formed was bonded to a 14-pin-DIP frame (42 alloy), and an aluminum electrode on the chip surface and a lead frame were wire-bonded with a 30 μmφ gold wire. Thereafter, the epoxy resin composition was molded thereon under molding conditions of 175 ° C., 70 kgf / cm ² and a molding time of 120 seconds, and post-cured at 180 ° C. for 4 hours. The package was left in an atmosphere of 140 ° C./85% RH under a DC bias voltage of 5 V for 500 hours, and then the number of packages in which aluminum corrosion occurred was examined.

From the results shown in Tables 1 and 2, the epoxy resin composition for semiconductor encapsulation of the present invention gives a cured product having good moldability and excellent flame retardancy, reflow crack resistance and moisture resistance.
In addition, since the halogenated epoxy resin and antimony trioxide were not contained in the resin composition, it was confirmed that the resin composition had no adverse effect on the human body and environment.

[0048]

[Table 1]

[0049]

[Table 2]

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08K 3/24 C08K 3/24 H01L 23/29 H01L 23/30 R 23/31 (72) Inventor Toshio Shiohara 1-10 Hitomi, Matsuida-cho, Usui-gun, Gunma Prefecture Inside the Silicone Electronics Materials Research Laboratory, Shin-Etsu Chemical Co., Ltd. (72) Kazutoshi Tomiyoshi 1-10 Hitomi, Matsuida-machi, Usui-gun, Gunma Prefecture Shin-Etsu Chemical Co., Ltd. (72) Inventor Eiichi Asano 1-10 Hitomi, Matsuida-machi, Usui-gun, Gunma Prefecture 10 Silicone Electronic Materials Research Laboratory, Shin-Etsu Chemical Co., Ltd.

Claims (5)

[Claims] (A) an epoxy resin represented by the following general formula (1): (Wherein, R ¹ is the same or different atom or group selected from a hydrogen atom, an alkyl group having 1 to 4 carbon atoms and a phenyl group, and n is an integer of 0 to 10.) (B) Phenolic resin curing agent represented by general formula (2) (Where R ² is the same or different atom or group selected from a hydrogen atom, an alkyl group having 1 to 4 carbon atoms and a phenyl group, and m is an integer of 0 to 10.) (C) Molybdenum An epoxy resin composition for semiconductor encapsulation, comprising compound (D) an inorganic filler. 2. The semiconductor according to claim 1, wherein the molybdenum compound is added in an amount of 0.1 to 30 parts by weight and the inorganic filler is added in an amount of 400 to 1100 parts by weight based on 100 parts by weight of the total amount of the epoxy resin and the curing agent. Epoxy resin composition for sealing. 3. The epoxy resin represented by the general formula (1) has a resin melt viscosity of 0.1 to 2.5 poise measured at 150 ° C. by an ICI viscometer (cone plate type). Item 2. The epoxy resin composition for semiconductor encapsulation according to Item 1. 4. The phenolic resin represented by the general formula (2) has a resin melt viscosity of 0.1 to 1.2 poise at 150 ° C. measured by an ICI viscometer (cone plate type). Item 2. The epoxy resin composition for semiconductor encapsulation according to Item 1. 5. A semiconductor device encapsulated with a cured product of the epoxy resin composition for semiconductor encapsulation according to claim 1. Description: