Patent Application
20070281097
As follows is a more detailed description of the present invention.
[Curable Silicone Gel Composition]
—Component (A)—
The organopolysiloxane of the component (A) is a straight-chain diorganopolysiloxane represented by the general formula (1) shown below, wherein the principal chain is formed of repeating diorganosiloxane units and both molecular chain terminals are blocked with diorganovinylsiloxy groups (in this description, the term “organo group” refers to an unsubstituted or substituted monovalent hydrocarbon group that contains no aliphatic unsaturated bonds). In a curable silicone gel composition of the present invention, in order to improve the flux resistance, it is important that the component (A) that functions as the base polymer is a straight-chain siloxane chain structure formed of repeating bifunctional diorganosiloxane units, wherein all of the monofunctional siloxane units that constitute the molecular chain terminals contain a vinyl group bonded to the terminal silicon atom.
In the general formula (1), R represents an unsubstituted or substituted monovalent hydrocarbon group, excluding aliphatic unsaturated hydrocarbon groups such as alkenyl groups, and specific examples include alkyl groups such as a methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, cyclohexyl group, or heptyl group; aryl groups such as a phenyl group, tolyl group, xylyl group, or naphthyl group; aralkyl groups such as a benzyl group or phenethyl group; and halogenated alkyl groups such as a chloromethyl group, 3-chloropropyl group, or 3,3,3-trifluoropropyl group. n represents a number from 50 to 1,000.
The viscosity at 25° C. for this organopolysiloxane is typically within a range from 50 to 50,000 mPa·s, and is preferably from 100 to 10,000 mPa·s.
—Component (B)—
The non-functional organopolysiloxane of the component (B) is, for example, a straight-chain or branched non-functional organopolysiloxane, and preferably a straight-chain non-functional organopolysiloxane, represented by an average composition formula (2) shown below:
R1aSiO(4-a)/2 (2)
[wherein, R1 represents an unsubstituted or substituted monovalent hydrocarbon group, excluding aliphatic unsaturated hydrocarbon groups such as alkenyl groups, and a is a number that satisfies 0<a<3, and is preferably a number within a range from 1.95 to 2.2, and even more preferably from 1.98 to 2.05]. The term “non-functional” means that this organopolysiloxane contains no functional groups that contribute to the addition reaction between the alkenyl groups within the component (A) and the hydrosilyl groups (SiH groups) within the component (B).
Examples of the group R1 in the above formula include the same groups as those listed above in relation to the group R. Specific examples of the non-functional organopolysiloxane include diorganopolysiloxanes with both terminals blocked with triorganosiloxy groups (here, the term “organo group” is as defined above for the component (A)), such as dimethylpolysiloxane with both terminals blocked with trimethylsiloxy groups, copolymers of dimethylsiloxane and diphenylsiloxane with both terminals blocked with trimethylsiloxy groups, copolymers of dimethylsiloxane and methylphenylsiloxane with both terminals blocked with trimethylsiloxy groups, and dimethylpolysiloxane with both terminals blocked with dimethylphenylsiloxy groups.
The component (B) functions as a plasticizer within the composition of the present invention, and the hardness of the gel-like cured product generated upon curing the composition can be regulated by adjusting the blend quantity of the component (B). As the blend quantity of the component (B) is increased, the hardness of the resulting gel-like cured product decreases, yielding a softer product. If the blend quantity of the component (B) is too small, then the gel-like cured product cannot be softened adequately, whereas if the blend quantity is too large, the component (B) may exude from the gel-like cured product.
The viscosity of the component (B) at 25° C. is typically within a range from 20 to 10,000 mPa·s, and is preferably from 20 to 8,000 mPa·s, and even more preferably from 50 to 5,000 mPa·s. The viscosity of the component (B) is preferably lower than that of the component (A).
The blend quantity of the component (B) is preferably within a range from 10 to 200 parts by mass, and even more preferably from 50 to 100 parts by mass, per 100 parts by mass of the component (A).
—Component (C)—
The component (C) is an organohydrogenpolysiloxane containing an average of 3 or more hydrogen atoms bonded to silicon atoms (namely, hydrosilyl groups represented by SiH) within each molecule, and functions as a cross-linking agent within the composition of the present invention.
There are no particular restrictions on the molecular structure of the organohydrogenpolysiloxane of the component (C), and conventionally produced straight-chain, cyclic, branched-chain, or three dimensional network (resin-like) structures can be used, but the organohydrogenpolysiloxane must contain an average of 3 or more hydrogen atoms bonded to silicon atoms (hydrosilyl groups represented by SiH) within each molecule, and preferably contains at least 3 SiH groups within every molecule. The organohydrogenpolysiloxane typically contains an average of 3 to 200, and preferably from 3 to 150, and even more preferably from 4 to 100, SiH groups within each molecule.
Examples of this organohydrogenpolysiloxane include compounds represented by an average composition formula (3) shown below.
R2bHcSiO(4-b-c)/2 (3)
In the above formula (3), R2 represents an unsubstituted or substituted monovalent hydrocarbon group that contains no aliphatic unsaturated bonds, preferably contains from 1 to 10 carbon atoms, and is bonded to a silicon atom. Specific examples of suitable unsubstituted or substituted monovalent hydrocarbon groups of this group R2 include alkyl groups such as a methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, cyclohexyl group, octyl group, nonyl group, or decyl group; aryl groups such as a phenyl group, tolyl group, xylyl group, or naphthyl group; aralkyl groups such as a benzyl group, phenylethyl group, or phenylpropyl group; and groups in which a portion of, or all of, the hydrogen atoms in an aforementioned group have been substituted with a halogen atom such as a fluorine, bromine or chlorine atom, such as a chloromethyl group, chloropropyl group, bromoethyl group, or trifluoropropyl group. The unsubstituted or substituted monovalent hydrocarbon group of R2 is preferably an alkyl group or aryl group, and is most preferably a methyl group or phenyl group. Furthermore, b is a positive number within a range from 0.7 to 2.1, c is a positive number from 0.001 to 1.0, and b+c is a positive number within a range from 0.8 to 3.0. Moreover, b is preferably within a range from 1.0 to 2.0, c is preferably from 0.01 to 1.0, and b+c is preferably within a range from 1.5 to 2.5.
The average of 3 or more SiH groups within each molecule, which preferably includes at least 3 SiH groups within every molecule, may be located at the molecular chain terminals or at non-terminal positions within the molecular chain, or may also be located at both these positions. Furthermore, the molecular structure of this organohydrogenpolysiloxane may be any one of a straight-chain, cyclic, branched-chain or three dimensional network structure, although the number of silicon atoms within each molecule (namely, the polymerization degree) is typically within a range from 2 to 300, and is preferably from 3 to 150, and even more preferably from 4 to 100. The organohydrogenpolysiloxane is typically a liquid at room temperature (25° C.), with a viscosity at 25° C. that is typically within a range from 0.1 to 1,000 mPa·s, preferably from 0.5 to 1,000 mPa·s, and even more preferably from 5 to 500 mPa·s.
Provided the organohydrogenpolysiloxane of the component (C) contains an overall average of 3 or more SiH groups per molecule, the component may also include organohydrogenpolysiloxanes that contain only 1 or 2 SiH groups within each molecule.
Specific examples of the organohydrogenpolysiloxane of the component (C) include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, tris(hydrogendimethylsiloxy)methylsilane, tris(hydrogendimethylsiloxy)phenylsilane, methylhydrogencyclopolysiloxane, cyclic copolymers of methylhydrogensiloxane and dimethylsiloxane, methylhydrogenpolysiloxane with both molecular chain terminals blocked with trimethylsiloxy groups, copolymers of dimethylsiloxane and methylhydrogensiloxane with both terminals blocked with trimethylsiloxy groups, dimethylpolysiloxane with both terminals blocked with dimethylhydrogensiloxy groups, copolymers of dimethylsiloxane and methylhydrogensiloxane with both terminals blocked with dimethylhydrogensiloxy groups, copolymers of methylhydrogensiloxane and diphenylsiloxane with both terminals blocked with trimethylsiloxy groups, copolymers of methylhydrogensiloxane, diphenylsiloxane, and dimethylsiloxane with both terminals blocked with trimethylsiloxy groups, copolymers of methylhydrogensiloxane, methylphenylsiloxane, and dimethylsiloxane with both terminals blocked with trimethylsiloxy groups, copolymers of methylhydrogensiloxane, dimethylsiloxane, and diphenylsiloxane with both terminals blocked with dimethylhydrogensiloxy groups, copolymers of methylhydrogensiloxane, dimethylsiloxane, and methylphenylsiloxane with both terminals blocked with dimethylhydrogensiloxy groups, copolymers formed of (CH3)2HSiO1/2 units, (CH3)3SiO1/2 units, and SiO4/2 units, copolymers formed of (CH3)2HSiO1/2 units and SiO4/2 units, and copolymers formed of (CH3)2HSiO1/2 units, SiO4/2 units, and (C6H5)3SiO1/2 units, as well as compounds in which a portion of, or all of, the methyl groups in a compound described above have been substituted, either with other alkyl groups such as ethyl groups or propyl groups, or with phenyl groups or the like.
Of these compounds, organohydrogenpolysiloxanes in which the bifunctional siloxane units of the principal chain are all organohydrogensiloxane units, and in which both terminals are blocked with triorganosiloxy groups (here, an organo group is as defined above for the components (A) and (B), namely, an unsubstituted or substituted monovalent hydrocarbon group that contains no aliphatic unsaturated bonds), such as methylhydrogenpolysiloxane with both terminals blocked with trimethylsiloxy groups, are preferred as they provide favorable improvement in the flux resistance. Namely, organohydrogenpolysiloxanes represented by a general formula:
wherein R2 groups are as defined above, and m is an average number of 0 to 198, are preferred.
The blend quantity of the component (C) must be sufficient that for each 1 mol of vinyl groups bonded to silicon atoms within the component (A), the number of mols of hydrogen atoms bonded to silicon atoms within the component (C) is within a range from 0.4 to 3.0 mols, preferably from 0.4 to 2.5 mols, and even more preferably from 0.5 to 2.0 mols. If this quantity of hydrogen atoms is less than 0.4 mols, then the composition may not cure satisfactorily. Furthermore, if the quantity of hydrogen atoms exceeds 3.0 mols, then the heat resistance of the obtained cured product may deteriorate significantly.
—Component (D)—
There are no particular restrictions on the hydrosilylation reaction catalyst of the component (D), provided it accelerates the addition reaction (the hydrosilylation reaction) between the vinyl group-containing organopolysiloxane of the component (A) and the organohydrogenpolysiloxane of the component (C). Conventional hydrosilylation reaction catalysts can be used as the component (D). Specific examples of suitable catalysts include chloroplatinic acid, alcohol-modified chloroplatinic acid, coordination compounds of chloroplatinic acid with olefins, vinylsiloxane or acetylene compounds, tetrakis(triphenylphosphine)palladium and chlorotris(triphenylphosphine)rhodium. Of these, platinum-based compounds are preferred.
The quantity added of the component (D) need only be sufficient to be effective as a hydrosilylation reaction catalyst, and the quantity may be altered in accordance with the desired curing rate. Calculated as the mass of the catalytic metal element relative to the combined mass of the components (A), (B) and (C), the quantity of the catalyst is typically within a range from 0.1 to 1,000 ppm, preferably from 1 to 500 ppm, and even more preferably from 10 to 100 ppm. If this quantity is too large, then the reaction becomes undesirable from an economic viewpoint.
—Optional Components—
In addition to the components (A) through (D) described above, other optional components may also be added to the composition of the present invention as required, provided such addition does not impair the object of the present invention. For example, any of the conventional retarding agent compounds that exhibit a curing inhibiting effect on the addition reaction catalyst may be used. Specific examples of these compounds include phosphorus-containing compounds such as triphenylphosphine, nitrogen-containing compounds such as tributylamine, tetramethylethylenediamine and benzotriazole, as well as sulfur-containing compounds, acetylene-based compounds, compounds containing 2 or more alkenyl groups, hydroperoxy compounds, and maleic acid derivatives. The degree of the curing retardation effect caused by the retarding agent compound varies considerably depending on the chemical structure of the retarding agent used, and as a result, the quantity added is preferably adjusted to the optimum quantity for that particular retarding agent. Generally, if the quantity added is too small, then the long-term storage stability of the composition at room temperature may be poor, whereas if the quantity added is too large, there is a danger that the curing process may be impaired.
Examples of other optional components include inorganic fillers such as crystalline silica, hollow fillers, silsesquioxanes, fumed titanium dioxide, magnesium oxide, zinc oxide, iron oxide, aluminum hydroxide, magnesium carbonate, calcium carbonate, zinc carbonate, layered mica, carbon black, diatomaceous earth, and glass fiber; and fillers such as those described above that have undergone surface treatment with an organosilicon compound such as an organoalkoxysilane compound, organochlorosilane compound, organosilazane compound, or low molecular weight siloxane compound. Furthermore, silicone rubber powders and silicone resin powders may also be added.
Moreover, heat-resistant additives, pigments, dyes and moldproofing agents and the like may also be added as optional components.
The composition of the present invention forms a silicone gel upon curing. In this description, the term “silicone gel” describes a cured product with a low cross-linking density that comprises an organopolysiloxane as the main component, wherein the (¼ cone) penetration value (or consistency value) measured in accordance with JIS K2220 is within a range from 20 to 200, preferably from 15 to 200, and even more preferably from 20 to 150. This corresponds with a rubber hardness value measured in accordance with JIS K6301 of zero, indicating that the gel exhibits no effective rubber hardness (and is therefore soft). In this respect, the silicone gel of the present invention differs from so-called silicone rubber cured products (rubber-like elastomers).
The composition of the present invention is cured and converted to a silicone gel either by standing for approximately 24 hours at room temperature (approximately 25° C.), or by heating at a temperature of 40 to 150° C.
[Uses]
The composition of the present invention can be used for application and curing within locations where solder flux exists. In other words, although the trend towards minimizing the cleaning of substrates for electrical or electronic circuits such as IC substrates has increased the chances of residual solder flux existing on the surface of these substrates during semiconductor mounting processes, the composition of the present invention can still be applied and cured within these locations where solder flux exists, thereby forming a coating that seals, insulates and protects the underlying components, as well as absorbing mechanical vibrations and shocks. When used in this manner, the composition of the present invention exhibits excellent flux resistance, suffers no curing inhibition, and is able to seal and cover the substrate in a stable manner, with no loss in the excellent electrical insulation properties, excellent stability of electrical properties and superior flexibility expected of a silicone gel.
As a result, by curing the composition, the level of flux resistance of the silicone gel can be improved, and a silicone gel with excellent flux resistance can be formed.
Examples of the components of the flux include resin acids such as abietic acid, dextropimaric acid and levopimaric acid, as well as amine hydrochlorides and the like.
In the following description, viscosity values refer to values measured at 25° C. Furthermore, SiH/SiVi ratios refer to molar ratios.
(a) 100 parts by mass of a dimethylpolysiloxane with both molecular chain terminals blocked with dimethylvinylsiloxy groups, and with a viscosity of 5,000 mPa·s,
(b) 100 parts by mass of a dimethylpolysiloxane with both molecular chain terminals blocked with trimethylsiloxy groups, and with a viscosity of 100 mPa·s,
(c) 0.32 parts by mass of a methylhydrogenpolysiloxane with both molecular chain terminals blocked with trimethylsiloxy groups, and with a viscosity of 250 mPa·s (quantity of silicon atom-bonded hydrogen atoms=1.08% by mass, number of those hydrogen atoms within each molecule: an average of approximately 45) (the molar ratio of silicon atom-bonded hydrogen atoms within this component (c) relative to silicon atom-bonded vinyl groups within the component (a), namely SiH/SiVi=0.57),
(d) 0.1 parts by mass of 1-ethynylcyclohexanol, and
(e) a complex of chloroplatinic acid and divinyltetramethyldisiloxane, in sufficient quantity to provide a mass of platinum metal, relative to the combined mass of all the components, of 5 ppm were mixed together to prepare a composition A.
—Test for Evaluating Flux Resistance—
First, the prepared composition was cured by heating at 120° C. for 60 minutes, thus forming a transparent gel product. The hardness (penetration value) of this gel product was measured using a penetrometer prescribed in JIS K2220 (a ¼ scale cone).
Subsequently, a flux was prepared by dissolving abietic acid in toluene to form a 10% solution. This solution was added to the prepared composition in sufficient quantity that the concentration of abietic acid within the composition was 300 ppm, the composition was cured by heating at 120° C. for 60 minutes, and the hardness (penetration value) of the gel product was measured using a penetrometer prescribed in JIS K2220 (a ¼ scale cone).
The results are shown in Table 1.
With the exceptions of altering the quantity of the component (b) to 50 parts by mass, and altering the quantity of the component (c) to 0.34 parts by mass (SiH/SiVi=0.62), a composition B was prepared in the same manner as the example 1.
The flux resistance of the prepared composition was evaluated in the same manner as the example 1. The results are shown in Table 1.
With the exceptions of not adding the component (b), and altering the quantity of the component (c) to 0.22 parts by mass (SiH/SiVi=0.4), a composition C was prepared in the same manner as the example 1.
The flux resistance of the prepared composition was evaluated in the same manner as the example 1. The results are shown in Table 1.
100 parts by mass of a dimethylpolysiloxane with both molecular chain terminals blocked with trimethylsiloxy groups and with a viscosity of 1,000 mPa·s, in which 99.6 mol % of the diorganosiloxane units that constitute the principal chain are dimethylsiloxane units and the remaining 0.4 mol % are vinylmethylsiloxane units,
85 parts by mass of a dimethylpolysiloxane with both molecular chain terminals blocked with trimethylsiloxy groups, and with a viscosity of 1,000 mPa·s,
4.86 parts by mass of a dimethylpolysiloxane with silicon atom-bonded hydrogen atoms at both molecular chain terminals and with a viscosity at 25° C. of 18 mPa·s (quantity of silicon atom-bonded hydrogen atoms=0.13% by mass, number of those hydrogen atoms within each molecule: an average of 2) (SiH/SiVi=1.15),
0.1 parts by mass of 1-ethynylcyclohexanol, and
a complex of chloroplatinic acid and divinyltetramethyldisiloxane, in sufficient quantity to provide a mass of platinum metal, relative to the combined mass of all the components, of 5 ppm
were mixed together to prepare a composition D.
The flux resistance of the prepared composition was evaluated in the same manner as the example 1. The results are shown in Table 1.
100 parts by mass of a dimethylpolysiloxane with a viscosity of 800 mPa·s, in which of the two monofunctional siloxy units at the molecular chain terminals, an average of 0.58 units are blocked with dimethylvinylsiloxy groups and the remaining average of 1.42 units are blocked with trimethylsiloxy groups,
25 parts by mass of a dimethylpolysiloxane with both molecular chain terminals blocked with trimethylsiloxy groups, and with a viscosity of 1,000 mPa·s,
0.7 parts by mass of a methylhydrogenpolysiloxane with both molecular chain terminals blocked with trimethylsiloxy groups and with a viscosity of 100 mPa·s (quantity of silicon atom-bonded hydrogen atoms=0.51% by mass, number of those hydrogen atoms within each molecule: an average of approximately 16) (the molar ratio of silicon atom-bonded hydrogen atoms within this component relative to the above vinyl groups, namely SiH/SiVi=0.94),
0.1 parts by mass of 1-ethynylcyclohexanol, and
a complex of chloroplatinic acid and divinyltetramethyldisiloxane, in sufficient quantity to provide a mass of platinum metal, relative to the combined mass of all the components, of 5 ppm
were mixed together to prepare a composition E.
The flux resistance of the prepared composition was evaluated in the same manner as the example 1. The results are shown in Table 1.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-128537 | May 2006 | JP | national |
