JPH0337592B2 - - Google Patents

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 solvent-free one-component mounting resin composition. 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 many MOS/ICs, metallization on the back side of the pellet can be omitted by leading out the sub-electrode from the bonding 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, chip mounting equipment has become more automated and faster, and the requirements for the characteristics 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: -65 to 150℃ when heated to 350℃
Adhesion strength after thermal shock cycles, hot water treatment, etc. Thin film formation; Workability; Quantitative injection using a dispenser;
Screen printing and stamping properties. Curing properties: oven method, hot plate method, etc. Boyd: Low. Reliability: No defects in humidity resistance current 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 extremely unsatisfactory 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 in an electrically insulating thermosetting resin consisting of an inorganic filler, an epoxy resin, a curing agent, and a curing accelerator, the inorganic filler used is 80% by weight. %
The above particles have a particle size of 5μ or less, and 80% by weight have a particle size of 5μ or less.The epoxy resin is a mixture of a liquid alicyclic epoxy resin and a glycidyl type polyfunctional epoxy resin, and is The chemical halogen group is less than 300ppm (weight), the curing agent is finely powdered dicyandiamide, and the curing accelerator is a tertiary amine salt, so it has excellent ability to form a thin film of 10 to 30μ. We have significantly reduced the amount of halogen ions in hot water extraction (20-hour pressure test) to less than 100 ppm, further improving reliability. 1
It is now possible to cure at 450℃ for 10 seconds or shorter cycles, and the bonding process and mounting process can be performed simultaneously on a hot plate.It has particularly excellent tack-free properties, and can be used not only with the dispenser method. The present inventors have discovered that the present invention has many advantages, such as being able to be continuously applied over a long period of time to methods such as , screen printing, and stamping. As the electrically insulating filler used in the present invention, 80
More than % by weight is fine particles with a particle size of 5 μm. If the particle size is large, a uniform thin film cannot be obtained. Moreover, it must be compatible with epoxy resins, not absorb a large amount of resin, and must not contain ionic impurities such as alkali metal ions and halogens. Therefore, the surface of the filler may be appropriately treated with a surface treatment agent such as a silicone-based, fluororesin-based, or organic titanate-based agent. 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, silicic acid, zircon, 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/
It is within the range of 80 to 40/60 (capacity ratio). As the alicyclic epoxy resin used in the present invention,
Epoxycyclohexylmethyl-epoxycyclohexanecarboxylic acid ester, bis(epoxycyclohexylmethyl) succinic acid, adipic acid,
These include diesters of aliphatic dibasic acids such as sebacic acid, vinylcyclohexene dioxide, dicyclopentadiene dioxide, and lower alkyl derivatives thereof. Since the epoxy group of the alicyclic epoxy resin is not a terminal epoxy group but an internal epoxy group, acid anhydrides are particularly effective as curing agents, but amines are not so effective. However, when it is used in combination with a glycidyl-type polyfunctional epoxy resin as in the present invention, this serves as the starting point for ring-opening polymerization, and it is thought that the curing reaction proceeds smoothly in the form of copolymerization of both. That is, although internal epoxy groups alone do not cure sufficiently with dicyandiamide, when they coexist with terminal epoxy groups, copolymerization between the two occurs, resulting in good curing. For the purpose of the present invention, epoxycyclohexylmethyl-epoxycyclohexane carboxylic acid ester type is particularly preferred since it has a high boiling point and low viscosity. One of the major features of alicyclic epoxy resin is that it essentially does not contain hydrolyzable halogen groups as impurities. The content of hydrolyzable halogen groups in the glycidyl type epoxy resin used in the present invention is desirably 1000 ppm (preferably 600 ppm) or less, and two or more resins may be appropriately blended to achieve this level. You may adjust it accordingly. Since many ordinary epoxy resins have an excessive amount of hydrolyzable halogen groups and are not suitable for the purpose of the present invention, it is desirable to perform appropriate purification before use. Furthermore, the epoxy resin used in the present invention needs to contain 2.5 or more epoxy groups per molecule. The number of epoxy groups per molecule is 2.0 as in the normal Epibis type, which has sufficient heat resistance.
This is undesirable because rapid curing cannot be achieved. However, 3
It is also possible to use a combination of a functional or higher functionality and a difunctional one to have 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, triglycidyl ether of trihydroxybiphenyl, tetraglycidyl ether of tetrahydroxybiphenyl, tetraglycidyl ether of tetrahydroxybisphenol F,
Tetraglycidyl ether of tetrahydroxybenzophenone, epoxidized novolak, epoxidized polyvinylphenol, triglycidyl isocyanurate, triglycidyl cyanurate, triglycidyl S-triazine, triglycidyl aminophenol, tetraglycidyl diaminodiphenyl Tri- or more polyfunctional epoxy resins such as methane, tetraglycidyl metaphenylene diamine, and tetraglycidyl pyromellitic acid, and bifunctional epoxy resins blended therewith, such as diglycidyl resorcin, diglycidyl 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 these condensation type resins. In addition, special types of allylated polyphenols, such as epoxidized polyphenols based on mono- to tri-nuclear bodies with peracid, which have a glycidyl ether group and a glycidyl group substituted with a nucleus, also meet the above conditions. If it is fulfilled, it can be used in the same way. In the present invention, an alicyclic epoxy group that essentially does not contain a hydrolyzable halogen group as an impurity and a glycidyl type polyfunctional epoxy group containing this are mixed in a ratio of 90/10 to 40/60. This reduces the amount of hydrolyzable halogen groups in the resin as a whole.
The content should be 600 ppm, preferably 400 ppm or less. The curing agent used in the present invention must be latent, and dicyandiamide is most suitable. However, dicyandiamide is difficult to dissolve in the resin, so if it is coarse, it may settle, resulting in uneven dispersion and uneven curing. Therefore, dicyandiamide must be finely ground, preferably wet ground, to ensure uniform dispersion. It is preferable. It is not preferred to use dicyandiamide as a solution since a volatile solvent will be included in the composition. The particle size of the dicyandiamide used is preferably 350 mesh pass; otherwise, a uniform cured product may not be obtained and performance may vary, which is not preferable. The above-mentioned pulverization is essential for improving the reliability of mounting resin. 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 are trimethylene diamine, 1,
These include 8-diaza-bicyclo-(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, succinic acid, maleic acid,
These are polybasic acids such as itaconic acid, or polyhydric phenols such as resorcinol, pyrogallol, hydroquinone, bisphenol A, bisphenol F, bisphenol S, and low-molecular novolaks. The amount of these tertiary amine salts is desirably in the range of 0.1 to 10 parts per 100 parts (by weight, hereinafter the same) 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 these tertiary amine salts tend to absorb moisture and carbon dioxide before use, which tends to deteriorate their performance. 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 use it after purification. In order to stabilize the curability of the mount resin, it is preferable to use one within the above range. In the present invention, a defoaming agent, a surface treatment agent, etc. may be used as appropriate. As defoaming agents and surface treatment agents, silicone-based,
Any of fluororesin-based materials and organic titanate-based materials may be used. In any case, it is preferable that aromatic low-boiling point solvents are not included as much as possible. In addition, it is preferable that the material is not silicone-based so as not to cause contact failure. Alicyclic epoxy resin used in the present invention, curing agent,
In all curing accelerators, it is desirable that the content of ionic impurities such as Cl ions and Na ions is 10 ppm or less. However, these raw materials essentially do not contain hydrolyzable halogen groups like glycidyl-type epoxy resins, nor do they contain these ionic impurities, so they cannot be processed through normal processes such as distillation and recrystallization. By purification of the compound, a product sufficiently suitable for the purpose of the present invention can be obtained. 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 to a total volume of 25 ml. The absorbance of the obtained test solution at a wavelength of 460 mm 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, and add 100 mL of pure water.
After shaking for 2 hours, the aqueous layer is centrifuged and used as a test solution. Sodium ions are determined from the absorbance of the sample solution at a wavelength of 330.2 nm using a flameless atomic absorption spectrometer, and sodium ions contained as impurities are determined using a previously prepared calibration curve in comparison with a blank test. The method for quantifying hydrolyzable chlorine in epoxy resin is to dissolve 0.5 g of resin in 30 ml of dioxane, and then
Heat with 5 ml of 1NKOH-ethanol solution and reflux for 30 minutes, then measure the amount of chlorine ion generated.
Determine by titration with 0.01NAgNO ₃ and use it as the amount of hydrolyzable chlorine. The conventional measurement method was to heat and reflux a 0.1 NKOH-methanol solution for 15 minutes, but this method is not preferable for the purpose of the present invention because it gives a too small value for the amount of hydrolyzable chlorine. The method for measuring hydrothermally decomposable chlorine ions in the cured product using the pressure cracker test is as follows. Cure the mounting resin at 200℃ for 30 minutes,
Next, the cured product is pulverized. 2g of the obtained powder sample
Add 3 ml of ethanol to the decomposition crucible and 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 insulating resin paste 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 insulating resin paste 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 hydrolytically decomposable impurities, in the mounting resin composition must be extremely small. (3) Good high-temperature curability; can be cured in a sufficiently short cycle on a hot plate;
The chip mounting process can be significantly shortened. (4) Particularly good tack-free properties; long-term operation for stamping, screen printing, etc. is possible, and workability is excellent. (5) Other properties, such as high-temperature mount strength, must be no better than conventional products. Therefore, the insulating resin paste 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 As an alicyclic epoxy resin, 3,4-epoxycyclohexylmethyl-3,4 epoxycyclohexane carboxylic acid ester (viscosity: 4 poise/25
°C, epoxy equivalent; 140, number average molecular weight; 285, number of epoxy groups/molecule; 2.0, hydrolyzable chlor;
None) 80 parts, glycidyl type polyfunctional epoxy resin, epoxidized phenol novolak (number average molecular weight: 650, epoxy equivalent: 175,
Number of epoxy groups/molecule: 3.7, hydrolyzable chlorine group: 800 ppm) 20 parts, dicyandiamide 5.0 parts pre-pulverized with 350 mesh pass as a hardening agent,
Stir 0.5 part of triethylenediamine resorcinol salt as a curing accelerator and 0.01 part of a fluororesin antifoaming agent,
Make a uniform dispersion. Furthermore, more than 80% by weight has a particle size of 5μ.
Add 40 parts of the following amorphous silica powder and 60 parts of charcoal of 2μ or less and knead with a crusher, and finally pass through three laurels to obtain a uniform paste-like mount resin composition. The resulting paste-like mounting resin composition is spread in a vat to a liquid thickness of 20 mm or less, and defoamed in a vacuum chamber at room temperature under high vacuum of 5 mmHg or less.
The defoamed resin composition is automatically supplied quantitatively onto the lead frame by screen printing or stamping to mount the chip. Curing of the resin is achieved by a 20 second cycle at 350°C on a hot plate. The performance of various mounting resins is shown in Table 1. In addition, if the above-mentioned epoxy resin is used only with an alicyclic epoxy resin without a glycidyl type multifunctional epoxy resin, it may be difficult to cure it depending on the above-mentioned curing agent and curing accelerator. Therefore, it is undesirable. Example 2 The same alicyclic epoxy resin as in Example 1 was used, and the glycidyl type polyfunctional epoxy was triglycidyl ether of phloroglucin (number average molecular weight: 370, epoxy equivalent: 130, number of epoxy groups/molecule; 2.8, hydrolyzable chlorine group; 900ppm)
Use. The curing agent, curing accelerator, and antifoaming agent are the same as in Example 1. The filler used is a 1:1 mixture of 80% by weight or more of alumina powder with a particle size of 5 μm or less and zirconia with a particle size of 2 μm or less. The formulation, paste properties, curing conditions, and performance of the cured product are shown in Table 1. Comparative Example 1 Both the alicyclic epoxy resin and the glycidyl type polyfunctional epoxy resin were the same as in Example 1. Methylhexahydrophthalic anhydride is used as a curing agent, and pentamethylene diethylene triamine is used as a curing accelerator. The filler is the same alumina powder as in Example 2. The formulation, paste properties, curing conditions, and performance of the cured product are shown in Table 1. In this case, it is difficult to perform curing at high temperature in a short time, which is not desirable. That is, an extremely long curing cycle of more than 10 hours at 80 to 120°C is required. Comparative Example 2 In Example 1, the particle size of calcium carbonate was 1~
A mounting resin composition is obtained in exactly the same manner except that a 15 μm resin composition is used. When the obtained composition was formed into a thin film with a thickness of 10 μm, the thickness was partially nonuniform, and the chip mountability of the thin film was extremely insufficient.

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Claims (1)

[Claims] 1. An electrically insulating thermosetting resin paste consisting of an inorganic filler, an epoxy resin, a curing agent, and a curing accelerator, 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 paste is in liquid form. Epoxy resin is a mixture of liquid alicyclic epoxy resin and glycidyl type multifunctional epoxy resin, and the hydrolyzable halogen group is 300 ppm or less (by weight), and the curing agent is dicyandiamide, which accelerates curing. An insulating resin paste characterized in that the agent is a tertiary amine salt.