JP2001288338A - Epoxy resin composition and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an epoxy resin composition for sealing semiconductors excellent in curability, flame retardance, reliability of moisture resistance and solder resistance and high-temperature storage characteristics without containing a halogen-based flame retardant and an antimony compound. SOLUTION: This epoxy resin composition for sealing the semiconductors is characterized as consisting essentially of (A) an epoxy resin, (B) a phenol resin, (C) a curing accelerator, (D) an inorganic filler and (E) a metal complex prepared by coordinating a ligand selected from naphthenic acid, acetylacetonato, phthalocyanine and thiocyanic acid with a metal element selected from Co, Cu, Zn, Ni, Mn and Fe.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epoxy resin composition for semiconductor encapsulation which does not contain a halogen-based flame retardant and an antimony compound and has excellent flame retardancy, and a semiconductor device.

[0002]

2. Description of the Related Art Conventionally, electronic components such as diodes, transistors, and integrated circuits are mainly sealed with an epoxy resin composition. In order to impart flame retardancy to these epoxy resin compositions, a flame retardant containing a bromine atom and an antimony compound such as antimony trioxide, antimony tetroxide and antimony pentoxide are usually blended. However, with increasing awareness of environmental protection worldwide, there is an increasing demand for an epoxy resin composition having flame retardancy without using an organic compound or an antimony compound containing a bromine atom. Further, when a semiconductor device sealed with an epoxy resin composition containing a halogen-based flame retardant and an antimony compound is stored at a high temperature, a thermally decomposed halide is liberated from these flame retardant components and the semiconductor element is bonded. Epoxy resin which is known to corrode the semiconductor device and impair the reliability of the semiconductor device, and can achieve a flame retardant grade of UL-94 V-0 without using a halogen-based flame retardant and an antimony compound as a flame retardant. A composition is required. As described above, the corrosion resistance of the bonding portion (bonding pad portion) of the semiconductor element after storing the semiconductor device at a high temperature (for example, 185 ° C.) is called a high-temperature storage characteristic, and the high-temperature storage characteristic is improved. A method using diantimony pentoxide is disclosed in Japanese Patent Application Laid-Open No. 55-146950.
And a method of combining antimony oxide and an organic phosphine (JP-A-61-53321), and the like,
Although the effect has been confirmed, some types of epoxy resin compositions are unsatisfactory with respect to recent high levels of high-temperature storage characteristics required for semiconductor devices. To meet these requirements, various flame retardants have been studied. For example,
Metal hydroxides such as aluminum hydroxide and magnesium hydroxide, and boron-based compounds have been studied, but if they are not added in large amounts, the flame-retardant effect is not exhibited, and the curability may be reduced. .

In the current situation where surface mounting of semiconductor devices is becoming common, a semiconductor device that has absorbed moisture is exposed to a high temperature during soldering, and cracks occur in the semiconductor device due to the explosive stress of vaporized water vapor. Or peeling at the interface between the semiconductor element or the lead frame and the semiconductor encapsulating material causes defects that greatly impair electrical reliability, and prevention of these defects, that is, improvement of solder resistance, is a major issue. Had become. Furthermore, in response to recent environmental problems, there has been a trend toward eliminating lead contained in solder used for mounting semiconductor devices, and it is believed that the temperature of soldering will increase with this trend. It is believed that the solder resistance will be more severe. In order to improve the solder resistance, a large amount of the filler is blended to reduce moisture absorption, reduce thermal expansion, and increase strength. For this reason, low-viscosity epoxy resins and crystalline epoxy resins that are crystalline at room temperature but exhibit extremely low viscosity above the melting point are used. A method for preventing a decrease in fluidity during molding of a resin composition is generally adopted. Since a crystalline epoxy resin has a low glass transition temperature, a system that does not use a halogen-based flame retardant or an antimony compound is required to improve high-temperature storage characteristics. However, since a crystalline epoxy resin has low curability, it is difficult to use a flame retardant that causes curing inhibition. That is, there is a need for an epoxy resin composition that maintains flame retardancy, is excellent in curability and high-temperature storage characteristics, and does not use a halogen-based flame retardant and an antimony compound.

[0004]

SUMMARY OF THE INVENTION The present invention relates to an epoxy for semiconductor encapsulation which does not contain a halogen-based flame retardant and an antimony compound and has excellent curability, flame retardancy, moisture resistance reliability and solder resistance, and high-temperature storage characteristics. A resin composition and a semiconductor device using the same.

[0005]

The present invention provides (A) an epoxy resin, (B) a phenolic resin, (C) a curing accelerator,
(D) inorganic filler, (E) Co, Cu, Zn, Ni, M
An epoxy resin for semiconductor encapsulation comprising, as an essential component, a metal complex in which a metal element selected from n and Fe is coordinated with a ligand selected from naphthenic acid, acetylacetonate, phthalocyanine and thiocyanic acid. A semiconductor device comprising a composition and a semiconductor element encapsulated with the composition.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The epoxy resin used in the present invention refers to all monomers, oligomers and polymers having two or more epoxy groups in one molecule, and their molecular weight and molecular structure are not particularly limited. For example, biphenyl type epoxy resin, bisphenol type epoxy resin,
Stilbene epoxy resin, naphthol epoxy resin, phenol novolak epoxy resin, cresol novolak epoxy resin, triphenolmethane epoxy resin, alkyl-modified triphenolmethane epoxy resin, epoxy resin containing triazine nucleus, dicyclopentadiene-modified phenol type Examples include an epoxy resin and a phenol aralkyl type epoxy resin (having a phenylene skeleton, a biphenylene skeleton, and the like), and these may be used alone or in combination. Of these, a crystalline epoxy resin having a melting point of less than 150 ° C. is preferable. 150
If the temperature exceeds ℃, the melted mixture does not melt sufficiently and cannot be uniformly dispersed, so that the molded product of the epoxy resin composition using the melt mixture becomes non-uniform, and the performance of the semiconductor device is reduced because the strength is different depending on each part. Is not preferred. Examples of the crystalline epoxy resin satisfying these conditions include a biphenyl type epoxy resin represented by the general formula (1), a bisphenol type epoxy resin represented by the general formula (2), and a stilbene type epoxy resin represented by the general formula (3). .

Embedded image (R ₁ in the formula represents an alkyl group having 1 to 6 carbon atoms, which may be the same or different; m is an integer of 0 to 4)

[0007]

Embedded image

[0008]

Embedded image (R ₄ in the formula represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, they may be the same or different .R ₅
Represents an alkyl group having 1 to 6 carbon atoms, which may be the same or different. m is an integer from 0 to 4)

The biphenyl type epoxy resin represented by the general formula (1) includes, for example, 4,4'-dihydroxybiphenyl, 4,4'-dihydroxy-3,3 ', 5,5'-tetramethylbiphenyl, 4,4 '-Dihydroxy-3,
3′-ditert-butyl-6,6′-dimethylbiphenyl, 2,2′-dihydroxy-3,3′-ditert-butyl-6,6′-dimethylbiphenyl, 4,4′-
Dihydroxy-3,3'-ditert-butyl-5,
Glycidyl etherified products of 5′-dimethylbiphenyl or 4,4′-dihydroxy-3,3 ′, 5,5′-tetratert-butylbiphenyl (including isomers having different substitution positions) are exemplified.

As the bisphenol type epoxy resin represented by the general formula (2), for example, bis (4-hydroxyphenyl) methane, bis (3-methyl-4-hydroxyphenyl) methane, bis (3,5-dimethyl-4-) Hydroxyphenyl) methane, bis (2,3,5-trimethyl-4)
-Hydroxyphenyl) methane, 1,1-bis (3 ′,
5'-dimethyl-4'-hydroxyphenyl) ethane,
2,2-bis (4′-hydroxyphenyl) propane,
2,2-bis (3′-methyl-4′-hydroxyphenyl) propane, 2,2-bis (3 ′, 5′-dimethyl-)
4'-hydroxyphenyl) propane, 2,2-bis (3'-tert-butyl-4'-hydroxyphenyl) propane, or bis (2-tert-butyl-5-
Glycidyl ether compounds such as methyl-4-hydroxyphenyl) sulfide.

As the stilbene type epoxy resin of the general formula (3), for example, 3-tert-butyl-4,4'-
Dihydroxy-5,3'-dimethylstilbene, 3-tert-butyl-4,4'-dihydroxy-3 ', 6-
Dimethyl stilbene, 3-tert-butyl-2,4 '
-Dihydroxy-3 ', 5', 6-trimethylstilbene, 3-tert-butyl-4,4'-dihydroxy-
3 ′, 5 ′, 6-trimethylstilbene, 3-tert-butyl-4,4′-dihydroxy-3 ′, 5,5′-
Trimethylstilbene, 4,4'-dihydroxy-3,
3'-dimethylstilbene, 4,4'-dihydroxy-
3,3 ′, 5,5′-tetramethylstilbene, 4,
4'-dihydroxy-3,3'-ditertiarybutylstilbene, 4,4'-dihydroxy-3,3'-ditertiarybutyl-6,6'-dimethylstilbene, 2,
2'-dihydroxy-3,3'-ditert-butyl-
6,6′-dimethylstilbene, 2,4′-dihydroxy-3,3′-ditert-butyl-6,6′-dimethylstilbene, 2,2′-dihydroxy-3,3 ′,
5,5'-tetramethylstilbene, 4,4'-dihydroxy-3,3'-ditert-butyl-5,5'-dimethylstilbene, or 4,4'-dihydroxy-3,
Glycidyl ether compounds such as 3 ′, 5,5′-tetratert-butylstilbene (including isomers having different substitution positions) are exemplified.

Among them, 4,4'-dihydroxybiphenyl, 4,4'-dihydroxy-3,3 ', 5,5'-tetramethyl are preferred in view of availability, performance, raw material price and the like. Biphenyl, bis (3,5-dimethyl-4-
Hydroxyphenyl) methane, bis (2,3,5-trimethyl-4-hydroxyphenyl) methane, 2,2-bis (3′-methyl-4′-hydroxyphenyl) propane, 2,2-bis (3 ′, 5'-dimethyl-4'-hydroxyphenyl) propane, glycidyl etherified bis (2-tert-butyl-5-methyl-4-hydroxyphenyl) sulfide (the above seven epoxy resins are hereinafter referred to as group a); 3-tert-butyl-2,
4'-dihydroxy-3 ', 5', 6-trimethylstilbene, 3-tert-butyl-4,4'-dihydroxy-3 ', 5', 6-trimethylstilbene, 3-tert-butyl-4,4 ' -Dihydroxy-3 ', 5
Glycidyl etherified product of 5′-trimethylstilbene (the above three types of epoxy resins are hereinafter referred to as group b), 4,
4′-dihydroxy-3,3 ′, 5,5′-tetramethylstilbene, 4,4′-dihydroxy-3,3′-ditert-butyl-6,6′-dimethylstilbene,
2,2′-dihydroxy-3,3′-ditert-butyl-6,6′-dimethylstilbene, 2,4′-dihydroxy-3,3′-di-tert-butyl-6,6′-dimethylstilbene, 2, 2'-dihydroxy-3,
3 ', 5,5'-tetramethylstilbene, or 4,
4'-dihydroxy-3,3'-ditert-butyl-
One or more selected from glycidyl etherified products of 5,5′-dimethylstilbene (the above six types of epoxy resins are hereinafter referred to as group c) are preferred.

Of the group a, the biphenyl type epoxy resin has a high viscosity reducing effect and is highly reactive.
Those containing a skeleton of -dihydroxybiphenyl are particularly preferred, and glycidyl etherified products of 4,4'-dihydroxybiphenyl are most preferred. In other group a, bis (3,5-dimethyl-4-hydroxyphenyl) methane, 2,2-bis (3 ′, 5′-dimethyl-)
4'-hydroxyphenyl) propane, bis (2-tert-butyl-5-methyl-4-hydroxyphenyl)
Glycidyl etherified sulfide is particularly preferred.
Further, in the stilbene type epoxy resin, a mixture of at least one selected from group b and one or more selected from group c,
It is preferable because the melting point becomes low. The mixing ratio, mixing method, and the like are not particularly limited. For example, there is a method of mixing stilbene-type phenols, which are raw materials of the stilbene-type epoxy resin, before glycidyl etherification, or a method of melt-mixing both stilbene-type epoxy resins. or,
In order to improve the moisture resistance reliability, it is desirable that the amount of chlorine ions, sodium ions, and other free ions contained in the crystalline epoxy resin used in the present invention is as small as possible.

The phenolic resin used in the present invention includes:
Monomers, oligomers, and polymers generally having two or more phenolic hydroxyl groups in one molecule are not particularly limited in molecular weight and molecular structure. For example, phenol novolak resin, cresol novolak resin, dicyclopentadiene-modified phenol Resins, terpene-modified phenol resins, triphenol methane resins, phenol aralkyl resins (having a phenylene skeleton, biphenylene skeleton, and the like), naphthol aralkyl resins, and the like, and these may be used alone or in combination. Of these, phenol novolak resins, dicyclopentadiene-modified phenol resins, phenol aralkyl resins, terpene-modified phenol resins, and the like are particularly preferable. The ratio of the number of epoxy groups in all epoxy resins to the number of phenolic hydroxyl groups in all phenolic resins is 0.8 to 0.8.
1.3 is preferred.

As the curing accelerator used in the present invention, any one can be used as long as it accelerates the curing reaction between the epoxy group and the phenolic hydroxyl group, and those generally used for a sealing material can be used. For example, 1,8-diazabicyclo (5,4,0) undecene-7, triphenylphosphine, 2-methylimidazole, tetraphenylphosphonium / tetraphenylborate and the like can be mentioned, and these may be used alone or as a mixture. .

As the inorganic filler used in the present invention, those generally used for a sealing material can be used. For example, fused silica, crystalline silica, talc, alumina, silicon nitride and the like can be mentioned, and these may be used alone or in combination. As a compounding amount, from the balance of moldability and solder crack resistance, 60 to 60% in all epoxy resin compositions
95% by weight is preferred. If it is less than 60% by weight, the solder cracking resistance decreases with an increase in water absorption, and if it exceeds 95% by weight, problems such as wire sweep and pad shift are caused, which is not preferable.

The metal complex used in the present invention acts as a flame retardant, and a flame retardant effect can be obtained by adding a small amount of the metal complex. As metal complexes, Co, Cu, Zn, Ni, Mn,
Naphthenic acid, acetylacetonate, phthalocyanine, a ligand selected from thiocyanic acid is coordinated to a metal selected from Fe, for example, cobalt naphthenate, cobalt acetylacetonate, copper acetylacetonate, zinc Acetyl acetonate and the like may be mentioned, and these may be used alone or as a mixture. Of these, cobalt naphthenate is preferred because it has particularly high flame retardancy and the amount of addition can be reduced. The flame retardant mechanism of the metal complex has the effect of suppressing the generation of flammable volatiles during combustion and the effect of promoting the carbonization of the cured resin component and forming a flame retardant layer that blocks oxygen on the surface of the cured product. It is believed that there is. The amount of the metal complex is preferably 0.001 to 10% by weight, more preferably 0.01 to 5% by weight, based on the entire epoxy resin composition. 0.001% by weight
If it is less than 10%, the flame retardancy is insufficient, and if it exceeds 10% by weight, the curability is undesirably reduced.

The epoxy resin composition of the present invention comprises (A)
In addition to the component (E), a flame retardant such as a brominated epoxy resin or antimony trioxide may be contained as necessary, but the stability of the electrical characteristics of the semiconductor device at a high temperature of 150 to 200 ° C. For applications required, the content of bromine atoms and antimony atoms is preferably less than 0.01% by weight in the total epoxy resin composition, and more preferably not completely contained. If either the bromine atom or the antimony atom is 0.01% by weight or more, the resistance value of the semiconductor device increases with time when left at a high temperature, and eventually the failure that the gold wire of the semiconductor element breaks may occur. appear.
Further, from the viewpoint of environmental protection, it is desirable that the content of each of the bromine atom and the antimony atom is less than 0.01% by weight, and that the content is as low as possible. The content of bromine atoms can be measured by elemental analysis such as fluorescent X-ray analysis and ion chromatography. The content of antimony atoms can be measured by elemental analysis such as atomic absorption analysis, emission analysis, X-ray fluorescence spectroscopy, and ion chromatography. The epoxy resin composition of the present invention comprises (A)
The component (E) is an essential component, but if necessary, a silane coupling agent, a coloring agent such as carbon black, a release agent such as natural wax and synthetic wax, and a low stress such as silicone oil and rubber. Various additives such as additives may be appropriately compounded. Further, the epoxy resin composition of the present invention is obtained by sufficiently mixing the components (A) to (E) and other additives uniformly using a mixer or the like, and then melt-kneading the mixture with a hot roll or a kneader. , After cooling and pulverized. Various electronic components such as semiconductor elements are encapsulated using the epoxy resin composition of the present invention, and semiconductor devices are manufactured by curing and molding using conventional molding methods such as transfer molding, compression molding, and injection molding. do it.

[0019]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto. The mixing ratio is by weight. Example 1 5.8 parts by weight of a biphenyl type epoxy resin having a structure represented by the formula (4) as a main component (melting point: 105 ° C., epoxy equivalent: 191 g / eq)

Embedded image

5.2 parts by weight of a phenol resin of the formula (5) (softening point: 75 ° C., hydroxyl equivalent: 174 g / eq.)

Embedded image Triphenylphosphine 0.2 parts by weight Fused spherical silica (average particle diameter 20 μm) 88.0 parts by weight Cobalt naphthenate 0.1 part by weight Carbon black 0.3 part by weight Carnauba wax 0.4 part by weight using a mixer at room temperature After mixing at a surface temperature of 90
The mixture was kneaded 30 times using two rolls at a temperature of 45 ° C. and a temperature of 45 ° C., cooled and pulverized to obtain an epoxy resin composition. The obtained epoxy resin composition was evaluated by the following method. Table 1 shows the results.

Evaluation method Spiral flow: Using a mold for measuring spiral flow according to EMMI-1-66, a mold temperature of 175 ° C.
The measurement was performed at an injection pressure of 70 kg / cm ² and a curing time of 2 minutes.
The unit is cm. Curability: mold temperature 175 ° C, injection pressure 70kg / c
m ² , a molding time of 2 minutes and a value obtained by measuring the Bacol hardness 10 seconds after opening the mold. Bending strength and elastic modulus during heating: Flexural strength at heating and bending elastic modulus during heating were measured (at 240 ° C.) according to JIS K 6911. The unit is N / mm ² . Flame retardancy: Using a transfer molding machine, mold temperature 17
A test piece (127 mm × 12.7 mm × 3.2 mm) was molded at 5 ° C., injection pressure of 70 kg / cm ² and curing time of 2 minutes, and post-cured at 175 ° C. for 8 hours, according to the UL-94 vertical method. Flame retardancy was determined. Moisture absorption: Using a transfer molding machine, mold temperature 17
A molded product having a diameter of 50 mm and a thickness of 3 mm was molded at 5 ° C., an injection pressure of 75 kg / cm ² , and a curing time of 2 minutes.
After curing for a time, the obtained molded article was heated to 85 ° C. and a relative humidity of 8
It was left for 168 hours in an environment of 5%, and the change in weight was measured to determine the moisture absorption. The unit is% by weight. Solder resistance: Using a transfer molding machine, mold temperature 1
75 ° C, injection pressure 75 kg / cm ² , curing time 2 minutes, 8
0pQFP (2 mm thick, chip size 9.0 mm × 9.
0 mm), and was post-cured at 175 ° C. for 8 hours. The obtained package was left at 85 ° C. and a relative humidity of 85% for 168 hours, and then immersed in a 240 ° C. solder bath for 10 seconds.
Observing the package with a microscope, the crack occurrence rate [(number of external crack occurrence packages) / (total number of packages) × 1
00] was calculated. Units%. The ratio of the peeled area between the semiconductor element and the cured product of the epoxy resin composition was measured using an ultrasonic flaw detector, and the peeling rate [(peeled area) / (semiconductor element area) × 100] was determined. Units%. High-temperature storage characteristics: Using a transfer molding machine, a mold temperature of 175 ° C., an injection pressure of 70 kg / cm ² , a curing time of 2 minutes, and a 16 pDIP (chip size of 3.0 mm × 3.5 m)
m) was molded, post-cured at 175 ° C. for 8 hours, and subjected to a high-temperature storage test (185 ° C., 1000 hours). A package in which the electric resistance between wirings increased by 20% from the initial value was determined to be defective. . The treatment time in the thermostatic bath, which became 8 or more out of 15 pieces, was indicated as high-temperature storage characteristics. If this time is long, it indicates that the high-temperature stability is excellent. The unit is Hr. Bromine atom, antimony atom content: pressure 60 kg / cm
^The resulting molded product was compression-molded to a diameter of 40 mm and a thickness of 5 to 7 mm in ² , and the content of bromine atoms and antimony atoms in all the epoxy resin compositions was quantified using a fluorescent X-ray analyzer. The unit is% by weight.

Examples 2 to 7, Comparative Examples 1 to 4 According to the formulations shown in Tables 1 and 2, an epoxy resin composition was obtained in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2. The properties of the epoxy resin and phenol resin used in the examples and comparative examples are shown below. A stilbene-type epoxy resin having a structure represented by the formula (6) as a main component (melting point: 110 ° C., epoxy equivalent: 187 g / e)
q. ), A stilbene type epoxy resin having a structure represented by the formula (7) as a main component (melting point: 145 ° C., epoxy equivalent: 230 g / e)
q. ), Ortho-cresol novolak type epoxy resin (softening point 55 ° C., epoxy equivalent 196 g / eq.), Brominated bisphenol A type epoxy resin (epoxy equivalent 3
65 g / eq. , Bromine content 48% by weight), phenol novolak resin (softening point 80 ° C, hydroxyl equivalent 104g /
eq. )

Embedded image

[0023]

Embedded image

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

According to the present invention, an epoxy resin composition for encapsulating a semiconductor which does not contain a halogen-based flame retardant and an antimony compound and has excellent curability can be obtained. Excellent in moisture resistance reliability, solder resistance, and high temperature storage characteristics.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08K 5/07 C08K 5/07 5/098 5/098 5/56 5/56 H01L 23/29 H01L 23 / 30 R 23/31 F term (Reference) 4J002 CC04X CC05X CC06X CD04W CD05W CD06W CD07W CD11W CD13W CE00X DE147 DG038 DJ007 DJ017 DJ047 EE048 EG088 EU036 EU116 EW016 EY016 EZ008 FD017 FD090 FD138 FD14A FD01 AD02 AD02 AD07 AD02 AD07 A FA10 FA12 FB07 JA07 4M109 AA01 CA21 EA02 EB12 EC20

Claims (5)

[Claims] (A) an epoxy resin, (B) a phenolic resin, (C) a curing accelerator, (D) an inorganic filler, (E) C
A metal complex in which a ligand selected from naphthenic acid, acetylacetonate, phthalocyanine, and thiocyanic acid is coordinated to a metal element selected from o, Cu, Zn, Ni, Mn, and Fe is an essential component. Epoxy resin composition for semiconductor encapsulation. 2. The epoxy resin composition for semiconductor encapsulation according to claim 1, wherein the metal complex is cobalt naphthenate. 3. An epoxy resin having a melting point of less than 150 ° C. and at least one crystalline epoxy resin selected from the general formula (1), the general formula (2) or the general formula (3). The epoxy resin composition for semiconductor encapsulation according to the above. Embedded image (Wherein R ₁ represents an alkyl group having 1 to 6 carbon atoms, which may be the same or different, and m is an integer of 0 to 4). Embedded image (R ₄ in the formula represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, they may be the same or different .R ₅
Represents an alkyl group having 1 to 6 carbon atoms, which may be the same or different. m is an integer from 0 to 4) 4. The epoxy resin composition for semiconductor encapsulation according to claim 1, wherein the total amount of bromine atoms and antimony atoms contained in all the epoxy resin compositions is less than 0.01% by weight. 5. A semiconductor device comprising a semiconductor element encapsulated with the epoxy resin composition for semiconductor encapsulation according to claim 1.