JP4729778B2 - Epoxy resin composition, prepreg, and copper-clad laminate using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an epoxy resin composition having excellent flame retardancy without using a halogen flame retardant, and exhibiting excellent heat resistance and dimensional stability, a prepreg, and a copper-clad laminate using the same. Is. In particular, the present invention relates to a copper clad laminate suitable for use in a rigid interposer of an IC package.
[0002]
[Prior art]
In the field of semiconductors, a trend of shifting from conventional surface mounting to area mounting is progressing due to progress in high-density mounting technology, and new packages such as BGA and CSP are appearing and increasing. Therefore, the rigid substrate for interposer has been attracting more attention than before, and the demand for a high heat resistance and low thermal expansion substrate has increased.
In general, in order to reduce the thermal expansion coefficient of a substrate, inorganic fillers, particularly fused silica, are widely used. However, conventionally used coarse-grained fused silica constitutes a substrate. The present inventors have confirmed that there is a problem that moisture stays in a space formed by a coarse filler sandwiched in a narrow gap between the glass substrate and the copper foil and solder heat resistance is lowered.
On the other hand, when fine fused silica is used, the above problem is solved, but the problem of silica aggregation occurs. Even when this agglomeration occurs, there is a problem in that an appearance defect occurs, or moisture stays in the space where the agglomerates are formed and the solder heat resistance is lowered. Japanese Patent Application Laid-Open No. 9-272155 discloses a technique using spherical silica having a particle size of 0.3 to 5 μm, but there is no description of an optimal resin composition for an interposer substrate, and there is no mention of the problem of aggregation. . According to the present inventors, even if spherical silica is used, there is a problem that appearance deteriorates when the aggregation occurs, or moisture stays in a space where the aggregate is formed and solder heat resistance is lowered.
On the other hand, the resin member used for these semiconductors is often required to have flame retardancy.
Conventionally, in order to impart this flame retardancy, it has been common to use halogen-based flame retardants such as brominated epoxy in epoxy resins. However, since dioxins may be generated from halogen-containing compounds, the use of halogen-based flame retardants has been avoided along with the recent serious environmental problems. A system has been required. Phosphoric flame retardants have attracted attention due to the demands of these times, and phosphoric acid esters and red phosphorus have been studied. However, these conventional phosphoric flame retardants are easily hydrolyzed and have poor reaction with resins. There existed a problem that heat resistance fell or a glass transition temperature fell.
[0003]
[Problems to be solved by the invention]
The present invention has been made to solve such problems, and is suitable for a rigid interposer having halogen-free and excellent flame retardancy, and excellent solder heat resistance due to high heat resistance, low thermal expansion and low water absorption. An epoxy resin composition, and a prepreg and a copper clad laminate using the same are provided.
[0004]
[Means for Solving the Problems]
The present invention realizes a polyfunctional epoxy resin and a phenolic resin-based curing agent that contributes to heat resistance, a phosphorus compound having a specific structure having flame retardancy and excellent hydrolysis resistance, and low thermal expansion and low water absorption, An epoxy resin composition suitable for a copper-clad laminate for interposers containing a specific spherical silica that does not cause aggregation as an essential component is the main technical point, and the above-mentioned purpose has been achieved by such a composition and process. .
[0005]
Specifically, (A) an epoxy resin having three or more epoxy groups in one molecule, (B) a phenol resin-based curing agent having three or more phenolic hydroxyl groups in one molecule, (C) 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and (D) spherical fused silica having an average particle size of 2 μm or less that has been surface-treated in advance with a coupling agent, are essential components. In order to obtain a prepreg characterized by being impregnated into a fiber base material and drying them, and further to obtain a prepreg, a spherical fused silica having an average particle size of 2 μm or less is surface-treated by a specific process. A prepreg characterized by being used. In addition, a copper-clad laminate obtained by heat molding using this prepreg.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Examples of the epoxy resin having three or more epoxy groups in one molecule used in the present invention include novolac epoxy resins such as orthocresol novolac epoxy resin, phenol novolac epoxy resin, bisphenol A novolac epoxy resin, and trishydroxy. Derivatives such as phenylmethane type epoxy resins and epoxy resins in which the corresponding aromatic rings are alkylated, glycidyl etherified products of 1,1,2,2-tetrakishydroxyphenylethane, dimers, trimers thereof, etc. Examples thereof include tetrakishydroxyphenylethane type epoxy resin. The epoxy resin is a reactive phosphorus compound described later, since 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide reacts with the epoxy group to reduce the epoxy group in the resin. In order to keep the glass transition temperature at a high level, it is essential to be a trifunctional or higher functional epoxy resin.
[0007]
In particular, among tri- or higher functional epoxy resins, novolac type epoxy resin (A1) and at least one epoxy resin (A2) selected from trishydroxyphenylmethane type epoxy resin and tetrakishydroxyphenylethane type epoxy resin , Trishydroxyphenylmethane type epoxy resin or tetrakishydroxyphenylethane type epoxy resin (A2) can increase the crosslink density to increase the glass transition temperature, while novolac type epoxy resin (A1) allows the epoxy resin of the above (A2) it drawback is that water absorption size and crosslink density brittleness due to excessively high in the this to prevent such reduction in adhesion. Among the novolak epoxy resins (A1), orthocresol novolac epoxy resins are particularly preferable because they can reduce water absorption.
[0008]
In the present invention, the proportion of the component (A) in the epoxy resin composition is preferably 10 to 50% by weight. If it is less than 10% by weight, the binder component is reduced, and the heat resistance, particularly the solder crack resistance as an interposer of an IC package is lowered. If it exceeds 50% by weight, the proportion of the filler decreases, thermal expansion and water absorption increase, and solder crack resistance as an IC package interposer decreases, which is not preferable. Here, the solder crack resistance as an interposer is caused by the interposer or indirectly in the solder crack resistance test according to the JEDEC mounting rank condition performed in the BGA or CSP using a rigid interposer. It means the resistance to cracks that occur due to the influence of properties, or interfacial peeling.
In addition, as an epoxy resin, you may mix | blend 30 weight% or less of epoxy resins other than (A) component, for example, a bisphenol A type epoxy resin.
[0009]
Next, examples of the phenol resin-based curing agent having three or more phenolic hydroxyl groups in one molecule of component (B) include phenol novolac, bisphenol A novolac, phenol aralkyl resin, etc. Phenol novolac, which is relatively small and can easily remove low-functional monomers, is preferred.
In the present invention, the component (B) is added so that the equivalent ratio of the epoxy group of the epoxy resin to the total of the phenolic hydroxyl group and other active hydrogen of the component (B) is 0.8 or more and 1.2 or less. Is preferred. Outside this range, a decrease in glass transition temperature and an increase in water absorption may cause a decrease in solder crack resistance as an IC package interposer and a decrease in moisture resistance reliability of the IC.
[0010]
Component (C) 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, which is a flame retardant component of the present invention, is reactive phosphorus in which hydrogen bonded to phosphorus reacts with an epoxy group It is a compound and does not hydrolyze like conventional phosphoric acid esters or red phosphorus to increase water absorption or decrease adhesion, and is an extremely excellent phosphorus flame retardant. The amount of component (C) added in the present invention is preferably 0.5 to 10% by weight with respect to the entire epoxy resin composition.
If the amount is less than 0.5% by weight, the flame retardant effect may be reduced. If the amount exceeds 10% by weight, the glass transition temperature is decreased and the water absorption rate is increased. Deterioration of moisture resistance reliability may occur.
[0011]
Component (D) of the present invention is a spherical fused silica having an average particle size of 2 μm or less that has been surface-treated with a coupling agent in advance. Spherical fused silica is superior to other fillers and is optimal for adding a large amount of filler to achieve both low thermal expansion and resin fluidity. Fine spherical silica with an average particle size of 2 μm or less tends to aggregate, and this aggregate may form a space at the interface of resin, glass cloth, copper foil, etc., and deteriorate the solder heat resistance. Since silica is surface-treated with a coupling agent in advance, such a problem does not occur.
[0012]
The surface treatment method in the present invention is not particularly limited as long as it does not generate aggregates, and is a conventional wet method, that is, a method of diluting a coupling agent in a solvent or the like and mixing a filler, or Thereafter, a drying method, a dry method, that is, a method of spraying the coupling agent while stirring the filler with a mixer, and the like are performed. Among these, in the process of dissolving the epoxy resin composition in a solvent to obtain a varnish, applying it to a fiber base material and drying to obtain a prepreg, as a spherical fused silica surface-treated with a coupling agent at the time of varnish preparation, the average If a slurry-like product obtained by mixing a spherical fused silica having a particle size of 2 μm or less, a coupling agent and a solvent and reacting by heating is blended, the surface treatment of the spherical fused silica is performed extremely effectively.
[0013]
A coupling agent in spherical fused silica having an average particle diameter of 2 μm or less that has been surface-treated in advance with a coupling agent is a silane coupling agent, a silicone oil cup having two or more repeating units of siloxane bonds, and having an alkoxy group Silicon-based coupling agents such as ring agents, titanate-based coupling agents, and the like can be mentioned, and silicon-based coupling agents are preferable from the viewpoint of improving the wettability of the epoxy resin and fused spherical silica surfaces. Specifically, an epoxy silane coupling agent, an amino silane coupling agent, a ureido silane coupling agent, a mercapto silane coupling agent, a disilazane, a silicone oil type cup having two or more repeating units of siloxane bond and having an alkoxy group. Examples include at least one selected from the group consisting of ring agents. In particular, when an epoxy silane coupling agent, an amino silane coupling agent, and a silicone oil coupling agent having two or more repeating units of siloxane bond and having an alkoxy group are used in combination, the coupling agent is efficiently applied to the silica surface. To settle. In these cases, the ratio of the coupling agent is generally 0.1 part or more and 10 parts or less with respect to 100 parts of spherical fused silica (hereinafter, all “parts” represent parts by weight).
[0014]
When the above-mentioned spherical fused silica, coupling agent, and solvent are mixed and reacted by heating to form a slurry, the heating temperature is preferably between 50 ° C and 120 ° C. When the reaction is carried out at a temperature in this range, the reaction between the silanol on the silica surface and the coupling agent occurs selectively. If the temperature is lower than this range, the reaction becomes slow. The mixing ratio of the spherical fused silica, the coupling agent, and the solvent can be arbitrarily set, but the coupling agent is usually 0.1 part or more and 10 parts or less, and the solvent is 10 parts or more and 200 parts per 100 parts by weight of the spherical fused silica. Or less. Outside this range, the efficiency of the surface treatment may decrease. The slurry after the surface treatment is once filtered and redispersed in a different solvent before drying, or the solvent can be reduced by decantation as necessary. However, when this method is used, it is preferable to mix the surface-treated spherical fused silica slurry with other components without drying in order to prevent re-aggregation.
[0015]
In any method, when a coupling agent is used for the surface treatment, it is included in the present invention to use water, acid, alkali or the like as necessary in order to promote the reaction between the coupling agent and silica silanol. It is. Spherical fused silica having an average particle size of 2 μm or less accounts for 50% by weight or more in the epoxy resin composition because thermal expansion and water absorption are reduced. However, if it exceeds 90% by weight, the proportion of the inorganic filler in the epoxy resin composition is too large, and operations such as impregnation become difficult. Moreover, you may use another filler in the range which does not disturb a characteristic as needed. In this case, conventionally known fillers including spherical silica other than spherical fused silica having an average particle diameter of 2 μm or less that has been surface-treated in advance with the coupling agent of the present invention, to the extent that characteristics such as solder heat resistance are not deteriorated, It can be used arbitrarily.
[0016]
If necessary, the epoxy resin composition of the present invention may contain additives other than the above components as long as the characteristics are not impaired. The epoxy resin composition of the present invention can be applied to a substrate as a varnish using a solvent or without a solvent to obtain a prepreg. As the substrate, glass woven fabric, glass nonwoven fabric, and other organic substrates can be used. A fiber base is impregnated with the epoxy resin composition of the present invention and dried to obtain a prepreg, and one or a plurality of the prepregs are thermoformed together with a copper foil to obtain a copper-clad laminate. These prepregs and copper clad laminates are also included in the present invention.
[0017]
【Example】
Reference example 1
60 parts of spherical fused silica having an average particle size of 0.5 μm was put into a Henschel mixer, and 0.5 parts of γ-glycidoxypropyltrimethoxysilane and a silicone oil type coupling agent A (Nihon Unicar MAC2101) were added while stirring. One part was added in small portions. After completion of the addition, the mixture was stirred for 5 minutes and taken out.
Orthocresol novolak epoxy resin (Epiclon N-665 manufactured by Dainippon Ink & Chemicals, Inc.) 25 parts, phenol novolac (softening point 105 ° C.) 9.5 parts, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10- After dissolving 0.03 part of 2-phenyl-4-methylimidazole in a mixed solvent of methyl ethyl ketone and methyl cellosolve with respect to 5 parts of oxide (HCA manufactured by Sanko Chemical) and a total of 100 parts of the epoxy resin and the curing agent, Spherical fused silica having an average particle size of 0.5 μm, which had been surface-treated with a coupling agent in advance, was added to the solution little by little while stirring with a stirring stirrer blade. When all the components were mixed, the mixture was stirred for 10 minutes using a high-speed stirrer.
The prepared varnish is used to impregnate a glass cloth (thickness 180 μm, manufactured by Nitto Boseki) and dried in a heating furnace at 150 ° C. for 6 minutes to obtain a varnish solid content (a component excluding the glass cloth in the prepreg) of about 50% by weight. Prepreg was obtained. A predetermined number of the prepregs were stacked, and a copper foil having a thickness of 12 .mu.m was stacked on both sides, followed by heat-press molding at a pressure of 40 kgf / cm @ 2 and a temperature of 190 DEG C. for 120 minutes to obtain a double-sided copper-clad laminate.
[0018]
Reference example 2
1 part of γ-glycidoxypropyltrimethoxysilane and 70 parts of spherical fused silica with an average particle size of 1.5 μm are placed in a 3 L separable flask containing about 30 parts of methanol as a solvent in advance, and stirred at room temperature for 3 hours and then added. The solvent was removed by pressure filtration. The obtained solid was spread on a vat and dried for 2 hours with an explosion-proof dryer, and then treated with a ball mill for 3 hours to crush the agglomerates. Next, 12.5 parts of phenol novolac epoxy resin (Epiclon N-775 manufactured by Dainippon Ink and Chemicals), 5 parts of bisphenol A novolac epoxy resin (softening point 70 ° C., epoxy equivalent 201), phenol novolac (softening point 105 ° C.) 8. 2-phenyl-4 for 5 parts, 3.5 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (HCA manufactured by Sanko Chemical) and a total of 100 parts of epoxy resin and curing agent amount -After dissolving 0.03 part of methylimidazole in a mixed solvent of methyl ethyl ketone and methyl cellosolve, the spherical fused silica with an average particle diameter of 1.5 μm, which was previously surface-treated with a coupling agent, was a little while stirring with a stirrer type stirring blade. Added in increments. When all the components were mixed, the mixture was stirred for 10 minutes using a high-speed stirrer to prepare a varnish.
The prepared varnish is used to impregnate a glass cloth (thickness 180 μm, manufactured by Nitto Boseki) and dried in a heating furnace at 150 ° C. for 6 minutes to obtain a varnish solid content (a component excluding the glass cloth in the prepreg) of about 50% by weight. Prepreg was obtained. A predetermined number of the prepregs were stacked, and a copper foil having a thickness of 12 .mu.m was stacked on both sides, followed by heat-press molding at a pressure of 40 kgf / cm @ 2 and a temperature of 190 DEG C. for 120 minutes to obtain a double-sided copper-clad laminate.
[0019]
Reference example 3
In a 3 L separable flask containing about 40 parts of methanol as a solvent in advance, 0.5 part of γ- (2-aminoethyl) aminopropyltrimethoxysilane and a silicone oil type coupling agent A (Nihon Unicar MAC2101) 0.1 80 parts of spherical fused silica having an average particle size of 0.5 μm was added and stirred at 90 ° C. for 1 hour to obtain a slurry. Next, 12.5 parts of tetrakishydroxyphenylethane type epoxy resin (Epicoat E1031S made by oil-based shell epoxy), 5.5 parts of phenol novolak (softening point 105 ° C.), 9,10-dihydro-9-oxa-10-phospha To 1.5 parts of phenanthrene-10-oxide (manufactured by Sanko Chemical Co., Ltd.) and 0.03 part of 2-phenyl-4-methylimidazole as a mixed solvent of methyl ethyl ketone and methyl cellosolve for a total of 100 parts of epoxy resin and curing agent After dissolution, the slurry containing spherical silica prepared earlier was added little by little while stirring with a stirring blade. When all the components were mixed, the mixture was stirred for 10 minutes using a high-speed stirrer to prepare a varnish.
The prepared varnish is used to impregnate a glass cloth (thickness 180 μm, manufactured by Nitto Boseki) and dried in a heating furnace at 150 ° C. for 6 minutes to obtain a varnish solid content (a component excluding the glass cloth in the prepreg) of about 50% by weight. Prepreg was obtained. A predetermined number of the prepregs were stacked, and a copper foil having a thickness of 12 .mu.m was stacked on both sides, followed by heat-press molding at a pressure of 40 kgf / cm @ 2 and a temperature of 190 DEG C. for 120 minutes to obtain a double-sided copper-clad laminate.
[0020]
Examples 8-14 and Comparative Examples 1-6
Double-sided copper-clad laminates were obtained in the same manner as in Reference Examples 1, 2, or 3 with the formulations shown in Tables 1 and 2. However, as for the surface treatment method of silica, A is the same as in Reference Example 1 , B is the same as Reference Example 2, and C is the same as Reference Example 3 .
The evaluation method is as follows. The evaluation results are shown in the lower column of Tables 1 and 2.
[0021]
The evaluation methods of the obtained double-sided copper-clad laminate are shown in (1) to (4), and the evaluation methods of BGA are shown in (5) and (6).
(1) A double-sided copper-clad laminate with a glass transition temperature thickness of 0.6 mm is etched all over, and a 10 mm × 60 mm test piece is cut out from the obtained laminate, and 3 ° C./min using a dynamic viscoelasticity measuring device. The tan δ peak position was taken as the glass transition temperature.
(2) Linear expansion coefficient A double-sided copper-clad laminate with a thickness of 1.2 mm is etched all over, a 2 mm x 2 mm test piece is cut out from the resulting laminate, and the linear expansion coefficient in the Z direction is 5 ° C using TMA. Measured at / min.
(3) Flame retardant property A double-sided copper clad laminate having a thickness of 0.6 mm was entirely etched, and the obtained laminate was measured by UL-94 standard and vertical method.
(4) Solder heat resistance After a double-sided copper-clad laminate with a thickness of 0.4 mm was prepared, eight test pieces were prepared by a method according to JIS C 6481, and a moisture absorption treatment was performed at 125 ° C. for 8 hours. The number of appearance abnormalities was examined by immersing in a solder bath at 260 ° C. for 120 seconds.
[0022]
{Circle around (5)} Package Warpage A double-sided copper clad laminate having a thickness of 0.4 mm produced in the example was subjected to circuit processing for BGA. Using EME-7720 manufactured by Sumitomo Bakelite as the circuit board (rigid interposer) and sealing material, the mold temperature is 180 ° C., the injection pressure is 75 kg / cm ² , the curing time is 2 minutes, and 225 pBGA (package size is 24 × 24 mm, thickness The silicon chip is 9 × 9 mm in size, the thickness is 0.35 mm, and the bonding pad of the chip and the circuit board is bonded with a gold wire with a diameter of 25 μm.) And molded at 175 ° C. for 8 hours Post-cured. After cooling to room temperature, the height displacement of the upper surface of the package was measured with a surface roughness meter in the diagonal direction from the gate portion of the package, and the maximum displacement value based on the gate portion was taken as the amount of warpage. The unit is μm.
(6) BGA solder crack resistance Eight packages obtained by the same method as in (5) above are allowed to stand for 240 hours in an environment of 85 ° C. and 60% relative humidity, and then subjected to IR reflow treatment according to the JEDEC method. went. The internal peeling after processing and the presence or absence of cracks were observed with an ultrasonic flaw detector, and the number of defective packages was counted. When the number of defective packages is n, n / 8 is displayed.
[0023]
The copper-clad laminate obtained by using the epoxy resin composition of the present invention has excellent flame retardancy despite the fact that no halogen compound is used, and is excellent in evaluation with a laminate alone and an IC package. In addition, it exhibits excellent solder heat resistance and extremely little warpage after molding.
[0024]
[Table 1]
[0025]
[Table 2]
[0026]
Note 1) Surface treatment method of silica: A is the same as in Example 1, B is the same as Example 2, and C is the same as Example 3.
2) Silicone oil type coupling agent A: Nippon Unicar MAC2101
3) Silicone oil type coupling agent B: Nihon Unicar MAC2301
4) Orthocresol novolac epoxy resin: Epichrome N-665 manufactured by Dainippon Ink and Chemicals, Inc.
5) Phenol novolac epoxy resin: Epicron N-775 manufactured by Dainippon Ink and Chemicals, Inc.
6) Tetrakishydroxyphenylethane type epoxy resin: Epicoat E1031S made of oil-based shell epoxy
7) Trishydroxyphenylmethane type epoxy resin: Epicoat E1032 made of oil-shell epoxy
8) Bisphenol A novolak epoxy resin: softening point 70 ° C., epoxy equivalent 201
9) Bisphenol A type epoxy resin: epoxy equivalent 250
10) Phenol novolak: softening point 105 ° C., hydroxyl group equivalent 104
11) Bisphenol A novolak: softening point 115 ° C., hydroxyl equivalent 129
12) Phenol aralkyl resin: XL-225 manufactured by Mitsui Chemicals
13) 9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (HCA manufactured by Sanko Chemical)
14) 2-Phenyl-4-methylimidazole: The amount is based on 100 parts of the total amount of epoxy resin and curing agent.
【The invention's effect】
The epoxy resin composition of the present invention has excellent flame retardancy without using a halogen-based flame retardant, and has characteristics of high heat resistance and low thermal expansion. Therefore, the copper clad laminate obtained from the epoxy resin composition of the present invention is excellent in solder heat resistance, can provide a rigid interposer for IC packages with little warpage, and can greatly contribute to related industries.

Claims (6)

An epoxy resin composition used for impregnating a base material to obtain a prepreg, comprising: (A) an epoxy resin having three or more epoxy groups in one molecule; and (B) three or more phenols in one molecule. Phenolic resin-based curing agent having a functional hydroxyl group, (C) 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and (D) an average particle size of 2 μm previously surface-treated with a coupling agent The following spherical fused silica is an essential component, and the component (A) is at least one epoxy resin selected from a novolac type epoxy resin (A1) and a trishydroxyphenylmethane type epoxy resin or a tetrakishydroxyphenylethane type epoxy resin ( An epoxy resin composition, which is a combination with A2). Coupling agent is an epoxy silane coupling agent, amino silane coupling agent, ureido silane coupling agent, mercapto silane coupling agent, disilazane, silicone oil type having two or more repeating units of siloxane bond and having an alkoxy group The epoxy resin composition according to claim 1, wherein the epoxy resin composition is at least one coupling agent selected from the group consisting of coupling agents. The epoxy resin composition according to claim 1 or 2 , wherein the component (B) is a phenol novolac. The epoxy according to any one of claims 1 to 3, wherein the component (D) is blended in a slurry-like product obtained by mixing spherical fused silica having an average particle size of 2 µm or less, a coupling agent and a solvent and subjecting the mixture to a heat reaction. Resin composition. A prepreg obtained by impregnating and drying a fiber base material with the epoxy resin composition according to any one of claims 1 to 4 . A copper-clad laminate obtained by heat-molding the prepreg according to claim 5 .