JPH0337591B2 - - Google Patents

Abstract

PURPOSE:To provide one-pack mounting electrical insulating thermosetting resin paste, consiting of an inorg. filler, an epoxy resin, a curing agent, a curing accelerator and a solvent. CONSTITUTION:A finely divided inorg. filler (A) (e.g. silica, ground limestone or zirconia) having such a particle size distribution that at least 80wt% of the powder is composed of particles having a particle size of 5mum or below, a liquid epoxy resin (B) (having a hydrolyzable halogen-contg. group content of 600wt. ppm or below and contg. an average of at least 2.5 epoxy groups per molecule), a curing agent (C) contg. at least 2.5 active hydrogen atoms per molecule (e.g. polyhydric phenol), a curing accelerator (D) composed of a tert. amine solt and a solvent (E) (pref. non-arom. solvent having a b.p. of 120-250 deg.C) are blended together in such a proportion as to give a ratio of an average epoxy equivalent of the epoxy resin to an average active hydrogen equivatent of the curing agent of 3 or below.

Description

[Detailed description of the invention]

The present invention relates to an electrically insulating thermosetting resin paste comprising an inorganic filler and a liquid epoxy resin. More specifically, the present invention relates to a resin composition for one-component mounting. Due to recent remarkable developments in the electronics industry, it has evolved into transistors, ICs, LSIs, and super LSIs.
As the degree of circuit integration in these semiconductor devices increases rapidly, it becomes possible to mass-produce them, and as the prices of semiconductor products using these devices fall, labor-saving, efficiency, and reduction in raw material costs during production have become important issues. I came. In the conventional method, a semiconductor component is produced by mounting a semiconductor element or chip on a substrate conductor and a lead frame using gold foil, and then sealing this with a hermetic seal. As an improvement method, a sealing process using thermosetting resin was developed, and along with this, a mounting process using conductive resin containing silver powder was implemented, which greatly contributed to improving productivity and reducing costs. I'm getting used to it. In this case, in most MOS/ICs, metallization on the back side of the pellet can be omitted by drawing out the sub-electrode from the bonding pad on the pellet. Therefore, instead of using an expensive conductive resin as the mounting resin, a relatively inexpensive non-conductive resin is sufficient, and the total cost can thereby be significantly reduced. The electrically insulating thermosetting resin paste of the present invention is suitable for such purposes. Recently, as chip mounting equipment has become more automated and faster, demands on the properties required for the one-component mounting resin used therein are becoming more stringent. The properties necessary for a mounting resin are as follows. Mount strength: Adhesion strength after heating at 350℃, heat shock cycle from -65 to 150℃, hot water treatment, etc. Thin film formation workability: quantitative injection using a dispenser, screen printing, stamping. Curing properties: open method, hot plate method, etc. Boyd: Low. Reliability: No defects in wet electrostatic test. That is, there should be no silver migration, no variation in device characteristics due to gases generated from the cured adhesive, and no corrosion of aluminum wiring due to ionic impurities such as halogens and alkali metals. Wire bonding properties: There should be no deterioration in bonding properties due to gas generated from the cured product, and no contamination due to bleeding. (8) Pellet crack: Good buffer against stress caused by the difference in thermal expansion with the lead frame (especially in the case of copper alloy). The biggest problem with conventional mounting resins of this type is as follows. It is difficult to form a uniform thin film of 10 to 30μ, especially 10 to 20μ. The epoxy resin used must contain a large amount of hydrolyzable halogen groups as impurities of 1000 ppm or more. For this reason, the amount of hot water extracted chlorine ions in the Plessyer Kutsker test (20 hours) is large, several hundred ppm or more, and is therefore insufficient in terms of reliability. In terms of workability and curing properties, there is insufficient support for labor saving and speeding up. As a result of various studies on these points, the present inventors found that inorganic fillers, epoxy resins, curing agents,
In the electrically insulating thermosetting resin paste consisting of a curing accelerator and a solvent, 80% by weight or more of the inorganic filler used has a particle size of 5 μm or less. If the particle size is larger than this, the ability to form a thin film is impaired and the pellets tend to tilt during curing. As an epoxy resin, it is liquid and has a low content of hydrolyzable halogen groups.
600ppm (weight, same hereinafter) or less, has 2.5 or more epoxy groups per molecule, has 2.5 or more active hydrogen per molecule as a curing agent, and has tertiary as a curing accelerator. It is an amine salt, and because the ratio of the epoxy equivalent of the epoxy resin to the active hydrogen equivalent of the curing agent is 3.0 or less, it has excellent ability to form a thin film of 10 to 30μ, and the amount of chlorine extracted with hot water is low. less than 100ppm,
Preferably, it can be significantly reduced to 50 ppm or less, which further improves reliability.
It is now possible to cure in a cycle of 10 seconds or shorter, and the bonding process and mounting process can be performed simultaneously on a hot plate, contributing to the shortening of the process and greatly improving performance. This led to the present invention. More than 80% by weight of the electrically insulating filler used in the present invention is fine particles with a particle size of 5 μm or less.
Furthermore, it is necessary that it has good compatibility with the epoxy resin, does not absorb a large amount of resin, and does not contain ionic impurities such as alkali metal ions and halogen ions. Therefore, the surface of the filler is treated with an appropriate surface treatment agent.
For example, it may be treated with silicone-based, fluororesin-based, organic titanate-based, etc. Further, washing may be performed with water, a solvent, etc. as appropriate. Any filler that satisfies the above conditions can be used in the present invention, but fillers that are as low cost as possible are preferred. Particularly preferred are crystalline or amorphous fused silica, heavy calcium carbonate, alumina, clay, talc, zirconium silicate, zirconia, and the like. Fillers and resins used in the present invention (including curing agents)
It is preferable that the mixing ratio (capacity) with the metal is as high as possible without deteriorating the performance. Usually 20/80
It is within the range of 40/60 (capacity ratio). The epoxy resin used in the present invention is liquid and has a hydrolyzable halogen group content of 600 ppm or less, preferably
It must be 400 ppm or less and must contain 2.5 or more epoxy groups per molecule. It goes without saying that the amount of ionic impurities such as halogen ions and alkali metal ions is 10 ppm or less. Hydrolyzable halogen group of epoxy resin
There are various methods to reduce the amount to 600 ppm or less, preferably 300 ppm or less, and one example is as follows. Epoxy resin is produced by reacting a polyactive hydrogen compound (polyhydric phenols, polybasic acids, etc.) with epihalohydrin using quaternary ammonium hydroxide as a catalyst, and then ring-closing the resulting halohydrin group with an alcoholic alkali. Production method. halohydrin groups remaining in epoxy resin,
A method for purifying epoxy resins in which hydrolyzable halogen groups are heated in an anhydrous state with an equivalent amount of alcohol to close the rings. A purification method in which the remaining halohydrin groups are removed in the form of Ag ⁺ by reacting with an equivalent amount of fatty acid silver salt in an anhydrous state. A method for producing an epoxy resin, in which polyphenols are previously allylized, and then the allyl groups are epoxidized with an organic peracid, such as p-chlorobenzoic acid. For the purpose of the present invention, resins with a small amount of hydrolyzable halogen groups obtained by any method can be used in exactly the same manner, and therefore there are no restrictions on the method of reducing the amount. As the epoxy resin used in the present invention, two or more types may be blended as appropriate to adjust to this level. Ordinary epoxy resins usually contain 1000 ppm or more. Therefore, it is not desirable for the purpose of the present invention to use ordinary commercially available epoxy resins as they are. Furthermore, the epoxy resin used in the present invention must contain 2.5 or more epoxy groups per molecule. It is not desirable that the number of epoxy groups per molecule is 2.0 as in the usual Epivis type because sufficient heat resistance and fast curing properties cannot be obtained. However, it is also possible to use a combination of trifunctional or higher functionality and bifunctional functionality to give an average functionality of 2.5 or more. Any epoxy resin that satisfies the above conditions can be used as the epoxy resin used in the present invention, but the following types are particularly preferred. Phloroglucinol triglycidyl ether, trihydroxyphenyl triglycidyl ether, tetrahydroxybiphenyl tetraglycidyl ether, tetrahydroxybisphenol F tetraglycidyl ether, tetrahydroxybenzophenone tetraglycidyl ether, epoxy oxidized novolac, epoxidized polyvinylphenol, triglycidyl isocyanurate, triglycidyl cyanurate,
3 or more polyfunctional epoxy resins such as triglycidyl S-triazine, triglycidyl aminophenol, tetraglycidyl diaminophenylmethane, tetraglycidyl metaphenylene diamine, tetraglycidyl pyromellitic acid, and the like; Difunctional epoxy resins to be blended with, such as diglycidyl resorcinol, diglycidyl bisphenol A, diglycidyl bisphenol F, diglycidyl bisphenol S, diglycidyl ether of dihydroxybenzophenone, diglycidyloxybenzoic acid, diglycidyl phthalic acid (o, m, p), diglycidyl hydantoin, diglycidyl aniline,
diglycidyl toluidine, etc., or a condensation type resin of these. In addition, special types include allylated polyphenols, such as No. 1
- Products containing glycidyl ether groups and nuclear-substituted glycidyl groups, such as trinuclear-based epoxidized products with peracids, can also be used in the same way if they meet the above conditions. . The curing agent used in the present invention needs to be polyfunctional, having 2.5 or more active hydrogen groups per molecule that react with epoxy groups and participate in crosslinking.
Such active hydrogen-containing compounds include polyhydric phenols, aromatic polybasic acids, and aromatic polyamines, and polyhydric phenols are particularly desirable from the viewpoint of curability and storage stability. The polyhydric phenols are preferably amorphous resinous substances that are initial condensates of phenols and aldehydes and contain as little free phenol as possible. For example, low-molecular liquid novolacs mainly composed of di- and trinuclear bodies obtained by reacting monovalent phenols such as phenol, cresol, and xylenol with formaldehyde under strong acidity in a dilute aqueous solution, and monovalent phenols. and polyfunctional aldehydes such as acrolein and glyoxal under acidic conditions, and initial condensates under acidic conditions of polyvalent phenols such as sosorcin, catechol, and hydroquinone with formaldehyde. Either can be used in the same way as long as the requirements are met. Examples of aromatic polybasic acids include polybasic acids such as pyromellitic anhydride and trimellitic anhydride, and 2 to 3 molecules thereof.
Polybasic acid derivatives linked by ester bonds with functional polyols, difunctional acid anhydrides such as maleic anhydride, phthalic anhydride, endomethylene anhydride tetrahydrophthalic anhydride, hexahydrophthalic anhydride, and the above polybasic acids. such as a eutectic mixture,
Any of them can be used in the same way as long as the above conditions are met. Among the above-mentioned polyphenols, novolak type ones are particularly preferred, and among these, those having a relatively low molecular weight, less free P, and a narrow molecular weight distribution are preferred. That is, Mn; 350-450, Mw/
Mn: 2.0-3.5, free P: 0.5% (weight) or less,
A material with a softening point (microscopic method) of 80 to 110°C is suitable. This type of resin has good compatibility and reactivity with epoxy resin, has a relatively low viscosity as a mixture, is highly functional, has good curability, and has excellent physical properties of the cured product. A major feature is that the performance is well balanced in all aspects, such as: The ratio of the average epoxy equivalent of the epoxy resin used in the present invention to the average active hydrogen equivalent of the curing agent needs to be 3.0 or less, preferably 1.5 or less.
While the epoxy resin essentially contains a hydrolyzable halogen group as described above, the curing agent essentially does not contain it. Therefore, in the composition of the present invention, the larger the blending ratio (weight) of the curing agent to the epoxy resin, the lower the overall content of halogen groups, which is advantageous. Moreover, in order for the cured product to exhibit sufficient physical properties, the molar ratio of epoxy groups/active hydrogen groups is desirably within the range of 0.8 to 1.2. On the other hand, since there is a technical limit to reducing the content of hydrolyzable halogen groups in the epoxy resin used, the ratio of the average epoxy equivalent of the epoxy resin used to the average active hydrogen equivalent of the curing agent used is 3.0 or less. , preferably 1.5 or less, both of the above conditions can be satisfied. As the ratio (weight) of the two becomes higher than this, the weight proportion of the epoxy resin in the mounting resin composition increases, and therefore the content of hydrolyzable halogen groups derived from the epoxy resin tends to increase. This is not preferable because it may significantly deteriorate its reliability. The upper limit of the content of chlorine groups extracted with hot water in the pressurization test (20 hours) of the cured resin composition for mounting is 100 ppm, preferably 50 ppm,
The lower the better. That is, by improving the purity of the epoxy resin and increasing the proportion of the curing agent used, it is attempted to improve the purity of the mounting resin composition. The curing accelerator used in the present invention is a salt of a tertiary amine, and at least one selected from the group of dimethylbenzylamine, tris(dimethylaminomethyl)phenol, alicyclic superbases, and imidazoles.
Salts of tertiary amines and polyhydric phenols and polybasic acids are desirable. Alicyclic superbases include trimethylenediamine, 1,8-diaza-
Picyclo-(5,4,0)undecene-7, dodecahydro-1,4,7,9btetraazaphenalene, and the like. Imidazoles are those in which a substituent such as methyl, ethyl, propyl, a long-chain alkyl group up to C17, or a phenyl group is introduced at the 2- and/or 4-position. Those that form salts with these tertiary amines include phthalic acid (o, m, p), tetrahydrophthalic acid, endomethylenetetrahydrophthalic acid, dimer acid, hexahydrophthalic acid, trimellitic acid, adipic acid, These are polybasic acids such as succinic acid, maleic acid, and itaconic acid, or polyhydric phenols such as resorcinol, pyrogallol, hydroquinone, bisphenol A, bisphenol F, bisphenol S, and low-molecular-weight novolaks. The amount of these tertiary amine salts is desirably in the range of 0.1 to 10 parts per 100 parts (by weight, the same applies hereinafter) of the epoxy resin.
If the amount is less than this, the accelerating effect will be insufficient, and if it is more than this, the curing will not be promoted so much, but there is a risk that the storage stability will deteriorate, so both are undesirable. Note that salts of these tertiary amines tend to absorb moisture and carbon dioxide before use, which tends to deteriorate their performance. ) Below, it is preferable that the amount of CO ₂ gas absorbed is 5% or less. Once it absorbs water,
Since it is difficult to sufficiently purify CO ₂ gas, it is generally not preferable to purify it before use. In order to stabilize the curability of the mount resin, it is preferable to use a resin within the above range. In the present invention, a defoaming agent may be used as appropriate. As the defoaming agent, silicone-based, fluorine-based, or other defoamers may be used. In any case, it is preferable that aromatic low-boiling point solvents are not included as much as possible. Also, it is preferable that the material is not silicone-based so as not to cause contact failure. The solvent used in the present invention has a boiling point of 120°C to 250°C.
℃ non-aromatic ones are preferable, such as lower alkyl monoethers, diethers, and monoether acetates of glycols such as cellosolves and carbitols. Aromatic materials are not preferred because they may contaminate lead wires and the like. In addition, if the boiling point is lower than this, it will easily volatilize during use and the viscosity and fluidity will fluctuate, and if it is higher than this, if it does not completely volatilize during the curing process, it will remain and deteriorate the physical properties of the cured product, so both are undesirable. do not have. The curing agent, curing accelerator, and solvent used in the present invention are Cl
The content of ionic impurities such as ions and Na ions is preferably 10 ppm or less. However, these raw materials essentially do not contain hydrolyzable halogen groups like epoxy resins, nor do they contain these ionic impurities, and cannot be purified through normal purification such as distillation or recrystallization. What is obtained is sufficiently suitable for the purpose of the present invention. The test method for ionic impurities is as follows. For chlorine ions, shake 15 g of a liquid sample with 20 ml of pure water for 2 hours, then centrifuge the aqueous layer and use it as a test solution. Next, test solution
Collect 15 c.c. with a whole pipette, add 4 ml of 6% iron alum aqueous solution and 2 ml of 0.3% thiocyanic acid/mercury ethanol solution, and dilute with pure water until the volume reaches 25 ml. The absorbance of the obtained test solution at a wavelength of 460 nm is measured using a spectrophotometer, and the concentration of chlorine ions contained as impurities is determined using a calibration curve prepared in advance in comparison with a blank test. For epoxy resins, mounting resin compositions, curing agents, etc., in the case of viscous liquids or solids, uniformly dissolve 15 g of the sample in 30 ml of toluene, add 100 ml of pure water, and add 100 ml of pure water.
After shaking for an hour, the aqueous layer is centrifuged to prepare a test solution, and the same procedure is repeated. For sodium ions, use a flameless atomic absorption spectrometer to measure the absorbance of the above test solution at a wavelength of 330.2 nm. In comparison with a blank test, determine sodium ions contained as impurities using a calibration curve created in advance. . The method for quantifying hydrolyzable chlorine in epoxy resin is to dissolve 0.5 g of the resin in 30 ml of dioxane, heat and reflux it with 5 ml of 1NKOH-ethanol solution for 30 minutes, and then determine the amount of chlorine produced using _0.02NAgNO3. Determine the amount of hydrolyzable chlorine. In addition, 0.1NKOH−
The conventional measuring method was to heat and reflux a methanol solution for 15 minutes, but this method is not preferable for the purposes of the present invention because it yields an underestimate of the amount of hydrolyzable chlorine. The method for measuring hydrothermally decomposable chlorine ions using the pressure cracker test is as follows. Mounting resin at 200℃, 30
Allow to cure for 1 minute, then crush the cured product. 2 g of the obtained powder sample was mixed with 3 ml of ethanol in a decomposition crucible.
ml and allow to soak thoroughly. Next, add 40ml of pure water, seal completely and treat at 125℃ for 20 hours. After treatment, centrifuge if necessary, and use the supernatant as the test solution.
The chloride ion concentration and sodium ion concentration in the test solution are determined according to the above method. The manufacturing process of the mounting resin composition of the present invention is as follows. First, predetermined amounts of epoxy resin, curing agent, curing accelerator, and solvent are each weighed out and kneaded to form a uniform solution. In this case, for kneading, an appropriate combination of conventional stirring tanks, crushers, triple rolls, ink mills, etc. may be used. Next, a predetermined amount of filler is weighed out and kneaded with the resin solution to form a completely uniform paste. In this case as well, a stirring tank, a crusher, three rolls, etc. are used in combination as appropriate. Next, the paste-like resin composition is weighed and distributed into predetermined containers, and defoamed in a vacuum chamber to obtain a product. In this case, if the mounting resin layer is thick, it will not be possible to remove bubbles sufficiently, so it is preferable to make the layer as thin as possible. The resin composition thus obtained needs to be stored and transported at a temperature of -15°C or lower. If the temperature is higher than this, the shelf life will be significantly reduced, which is not preferable. The mounting resin composition of the present invention has the following features compared to conventional products. (1) Excellent ability to form a uniform thin film. (2) High purity: The amount of ionic impurities, including those that are hydrolytically decomposable, in the mounting resin composition is extremely small. (3) Curing on a hot plate is possible in a sufficiently short cycle, and the chip mounting process can be significantly shortened. (4) Other properties such as reliability, workability, high-temperature mounting strength, etc. are superior to conventional products. Therefore, the mounting resin composition of the present invention is of extremely high industrial value and meets the needs of the electronics industry, which has recently been rapidly becoming more sophisticated. Examples will be described below. Example 1 Epoxidized phenol novolak (number average molecular weight: 550, epoxy equivalent: 175, number of epoxy groups/
Molecule: 3.1, hydrolyzable chlorine group: 500ppm) 60 parts (weight, same below), phenol novolak (number average molecular weight: 460, active hydrogen equivalent: 105, number of active hydrogens/molecule: 4.2, hydrolysable chlorine) (without base) 40 copies,
0.2 parts of resorcinol salt of tris(dimethylaminomethyl)phenol as a hardening accelerator, 6 parts of butyl cellosolve acetate as a solvent, and 0.01 part of a fluororesin antifoaming agent are stirred to form a uniform solution. Furthermore, as fillers, 40 parts of amorphous silica powder, of which 80% or more has a particle size of 5μ or less, and 60 parts of calcium carbonate, which has a particle size of 3μ or less, are added and kneaded in a crusher, and finally passed through three rolls to form a uniform paste. A resin composition for mounting is obtained. The resulting paste-like resin composition for mounting is spread in a part to a liquid thickness of 20 mm or less, and degassed in a vacuum chamber at room temperature under high vacuum of 5 mmHg or less.
The defoamed resin composition is divided into dispenser syringes, small containers, etc., and stored and transferred in a -15°C freezer. The obtained mounting resin composition is automatically supplied quantitatively onto the lead frame using a dispenser to mount the chip. At this time, the resin is cured in a tunnel furnace at 200℃ for 40 minutes.
Obtained by passing for 1 minute. The performance of various mounting resins is shown in Table 1. In addition, when the above-mentioned epoxy resin is commercially available without purification, the amount of hydrolyzable chloro groups is
It is 1200ppm, and if this is used as is, the amount of chlorine ions after hot water extraction will be 350ppm. This value is undesirable for precision electronic devices from the viewpoint of reliability. Example 2 As the epoxy resin, Epibis liquid epoxy resin (number average molecular weight: 400, epoxy equivalent: 195,
number of epoxy groups/molecule; 2.0, hydrolyzable chlorine group; 200 ppm) and triglycidyl ether of phloroglycine (number average molecular weight; 380, epoxy equivalent; 125, number of epoxy groups/molecule; 3.0, hydrolyzable chloride group) ;700ppm) at a ratio of 1.0 to 2.0 (by weight, the same applies hereinafter). The curing agent is resorcinol-based novolac (number average molecular weight: 300,
Active hydrogen equivalent: 85, number of active hydrogens/molecule: 3.5,
without hydrolyzable chlor). Filler is 80%
A 1:1 mixture of alumina and zirconia with a particle size of 5 μm or less is used. The curing accelerator and antifoaming agent are the same as in Example 1. The formulation, paste properties, curing conditions, and performance of the cured product are shown in Table 1. Example 3 The epoxy resin was made by epoxidizing allylated bisphenol A with peracid (number average molecular weight;
410, epoxy equivalent; 140, number of epoxy groups/molecule; 2.9, no hydrolyzable chlorine group) and Example 1
1.0/1.0 with epoxidized phenol novolak
Use a mixture of The thermally conductive filler, curing agent, curing accelerator, and antifoaming agent are the same as in Example 1. The formulation, paste properties, and performance of the cured product are shown in Table 1. Comparative Example 1 Only the Epibis liquid epoxy resin of Example 2 is used as the epoxy resin. The filler, curing agent, curing accelerator, and solvent are the same as in Example 1. combination,
The paste properties, curing agent conditions, and properties of the cured product are
As shown in the table. The curing properties and mounting strength under heat are clearly inferior and undesirable. Comparative Example 2 A paste mounting resin is obtained in exactly the same manner as in Example 1, except that calcium carbonate having a particle size of 1 to 15 μm is used. When a thin film of the obtained composition was formed to a thickness of 10 μm, the thickness was partially non-uniform, and the chip mountability of the thin film was extremely poor.

【table】

【table】

Claims (1)

[Claims] 1. An insulating resin paste consisting of an inorganic filler, an epoxy resin, a curing agent, a curing accelerator, and a solvent, in which 80% by weight or more of the inorganic filler is fine particles with a particle size of 5 μ or less, and the epoxy resin is liquid. , the content of hydrolyzable halogen groups is 600 ppm (weight) or less, the epoxy group is 2.5 or more per molecule on average, the curing agent has 2.5 or more active hydrogen per molecule, and the curing The accelerator is a salt of a tertiary amine, and the ratio of the average epoxy equivalent of the epoxy resin to the average active hydrogen equivalent of the curing agent is
An insulating resin paste characterized by being 3.0 or less.