JPH10226746A - Epoxy resin molding material for semiconductor sealing and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epoxy resin molding material for semiconductor sealing, being excellent in moldability such as hot hardness and improved in reflow crack resistance. SOLUTION: This material essentially consists of a polyfunctional epoxy resin (A) having at least 2.3 epoxy groups on the average per molecule, a curing agent (B) containing a modified phenolic resin obtained by reacting a phenol with a fused polycyclic aromatic hydrocarbon and a formaldehyde source and an inorganic filler (C) and satisfies the following requirements: the ratio X/Y is 0.8-1.2 (wherein X is the number of the epoxy groups of component A, and Y is the number of the hydroxyl groups of component B; the modified phenolic resin of component B has a melt viscosity of 5 poise or lower at 150 deg.C and a hydroxyl equivalent of 150 or below; and the content of component C is 80-93wt.% based on the entire material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epoxy resin molding material for semiconductor encapsulation, and more particularly to a molding material suitable for encapsulating a surface mount semiconductor and a semiconductor device sealed with a cured product of the molding material.

[0002]

2. Description of the Related Art Conventionally, epoxy resin molding materials have been widely used in the field of semiconductor encapsulation of transistors, ICs and the like. The reason for this is that the epoxy resin is balanced in various properties such as moldability, electrical properties, moisture resistance, heat resistance, mechanical properties, and adhesiveness to insert products.
In particular, a combination of an ortho-cresol novolak type epoxy resin and a phenol novolak curing agent has an excellent balance of these properties, and is widely used as a base resin of a molding material for semiconductor encapsulation.

[0003] In recent years, with the progress of high-density mounting of semiconductor parts on a printed wiring board, semiconductor packages have been used in conventional D-packages.
Pin insertion type packages such as IP (Dual In-line Package) have been reduced, and QFP (Quad
Flat Package), SOP (Small
Out-line Package), TQFP (Th
in Quad Flat Package), TSO
P (Small Out-line Package)
The number of small and thin surface-mounted packages, such as those described above, is increasing. The mounting method of the surface mount type package is different from the conventional pin insertion type package.Since it is temporarily fixed to the wiring board surface, it is soldered with a solder bath or reflow device, etc.
The entire package is exposed to the soldering temperature. As a result, when the semiconductor package absorbs moisture, the moisture absorbed rapidly evaporates and expands during soldering, peeling of the bonding interface and package cracking occur, and the phenomenon that the moisture resistance is greatly reduced is the largest phenomenon of the surface mount type package. Has become a problem. On the other hand, with respect to the method of molding a semiconductor package, automation is progressing in terms of labor saving, and moldability (releasability and heat hardness) is an important characteristic item as a requirement for a molding material.

[0004] In order to cope with such trends, improvement of molding materials has been actively promoted. In order to improve the package crack during reflow, the epoxy resin and the curing agent, which are resin components of the molding material, were reviewed, and as a result, biphenyl with better hygroscopicity and adhesiveness than conventional ortho-cresol novolak type epoxy resin Various molding materials containing a skeletal epoxy resin have been proposed (JP-A-64
-65116, JP-A-3-207714, etc.). At present, molding materials containing this biphenyl type epoxy resin have begun to be put to practical use for sealing surface mount packages, and have greatly contributed to the improvement of reflow resistance of surface mount packages.

[Problems to be solved by the invention]

[0005] The molding material containing the above biphenyl type epoxy resin is remarkably excellent in reflow resistance as compared with the molding material containing the conventional orthocresol novolak type epoxy resin, but the moldability (releasability, Hardness when hot)
Therefore, improvement is desired. The biphenyl type epoxy resin is an epoxy resin mainly composed of a bifunctional monomer, and therefore has a low heat hardness (soft) after molding. As a result, there is a serious problem that the mold is difficult to be removed from the mold and that the semiconductor element as an insert is cracked because the package is easily deformed.

[0006] From the above background, it has the same reflow resistance as a material containing a biphenyl type epoxy resin,
There is a strong demand for a molding material that is as excellent in moldability as a conventional orthocresol novolak type epoxy resin.

[Means for Solving the Problems]

To solve the above-mentioned problems, the present inventors have conducted intensive studies to find a material having high heat hardness and good moldability, but also excellent reflow resistance. It has been found that a combination of a functional epoxy resin and a specific curing agent and their compounding amounts, and a molding material containing an inorganic filler having a specific content can satisfy the above-mentioned requirements, and have completed the present invention. Was.

That is, the present invention provides: (A) a polyfunctional epoxy resin having an average number of epoxy groups in one molecule of 2.3 or more; (B) reacting a phenol, a condensed polycyclic aromatic hydrocarbon and a formaldehyde source. A curing material containing a modified phenolic resin obtained by the above method, wherein (C) an inorganic filler is an essential component, and the number of epoxy groups in component (A) is X, and the number of hydroxyl groups in component (B) is Y. X / Y = 0.8 to 1.2, the modified phenol resin in the component (B) has a melt viscosity at 150 ° C. of 5 poise or less and a hydroxyl equivalent of 150 or less; An epoxy resin molding material for semiconductor encapsulation, wherein the content of the component (C) is 80 to 93% by weight with respect to the entire molding material, and the semiconductor encapsulated by a cured product of the molding material. Device.

[0009]

DETAILED DESCRIPTION OF THE INVENTION (A) used in the present invention
The component epoxy resin is a polyfunctional epoxy resin having an average number of epoxy groups in one molecule of 2.3 or more. If specifically illustrated, a phenol novolak type epoxy resin, an orthocresol novolak type epoxy resin, an epoxy resin obtained by epoxidizing a novolak resin synthesized from phenols and aldehydes including a bisphenol A novolak type epoxy resin, Epoxidized co-condensed resin of dicyclopentadiene and phenols, epoxy resin having naphthalene ring, epoxidized naphthol aralkyl resin, trimethylolpropane type epoxy resin, terpene-modified epoxy resin, etc., alone or in combination of two or more It can be used in combination. These epoxy resins are produced by reacting a phenolic compound with epihalohydrin.
By controlling the molecular weight of the epoxy-based compound, the molecular weight of the epoxy resin can be almost arbitrarily controlled. Several grades with different molecular weights are commercially available for each epoxy resin. Among these, in order to achieve the present invention, it is an essential condition that the number of epoxy groups in one molecule is 2.3 or more on average. Although it is difficult to accurately determine the average number of epoxy groups in one molecule, the value specified in the present invention is the same as the number average molecular weight determined by gel permeation chromatography (GPC) using tetrahydrofuran as an eluent. This is a value obtained from the structural formula.

The modified phenol resin contained in the component (B) used in the present invention is obtained by reacting a phenol, a condensed polycyclic aromatic hydrocarbon and a formaldehyde source under an acid catalyst. A curing agent having a melt viscosity at 150 ° C. of 5 poise or less and a hydroxyl equivalent of 150 or less.

The condensed polycyclic aromatic hydrocarbon is a component contained in petroleum heavy oils or pitches, and these petroleum heavy oils or pitches may be used as a raw material for synthesis. Petroleum heavy oils or pitches include crude oil distillation residue, hydrogenolysis residue, catalytic cracking residue, naphtha or LPG
And a residue obtained by decompressing the residual oil under reduced pressure, extracting by solvent extraction, or heat-treating. Among them, the aromatic hydrocarbon fraction fa value and the aromatic hydrogen content Ha value Choose and use the one that is best for you. The petroleum heavy oils or pitches suitable for the present invention have a fa value of 0.40 to 0.95 and a Ha value of 0.2 to 0.8. Note that the fa value and the Ha value are values calculated by the following formulas.
The value can be determined by 1H-NMR. Fa value = Number of aromatic carbons in oil or pitch / total carbon number in oil or pitch Ha value = Number of aromatic hydrogens in oil or pitch / Total hydrogen number in oil or pitch Fa value is less than 0.40 If so, the aromatic content is reduced, and the effect of reducing the moisture absorption of the cured product is small.
If it is larger than 0.95, the reactivity with the formaldehyde component is undesirably low. For the Ha value, 0.2
A smaller size is not preferred because the amount of aromatic hydrogen reacting with the formaldehyde component is reduced and the reactivity is reduced. If it is more than 0.8, the strength of the cured product tends to be low, and therefore it is not preferable.

The number of condensed rings of the aromatic hydrocarbons constituting the petroleum heavy oils or pitches is not particularly limited, but is preferably a condensed polycyclic aromatic hydrocarbon having 2 to 4 rings. When the petroleum heavy oils or pitches contain a large amount of condensed polycyclic aromatic hydrocarbons having 5 or more rings, the resulting modified phenolic resin tends to have a high viscosity and a large hydroxyl equivalent, so that the present invention Not suitable for Further, when the petroleum heavy oils or pitches are mainly monocyclic aromatic hydrocarbons, the reactivity with formaldehyde is low, and the effect of modifying the resulting modified phenol resin is not sufficient.

As a formaldehyde source, paraformaldehyde, polyoxymethylene, trioxane and the like can be used. The mixing ratio of petroleum heavy oils or pitches to formaldehyde polymer is such that the number of moles of formaldehyde polymer in terms of formaldehyde is based on 1 mole of the value calculated from the average molecular weight of petroleum heavy oils or pitches. It is 1-15, More preferably, it is 3-11. When it is less than 1, the strength of the resulting modified phenol resin is low, such being undesirable. On the other hand, if it is larger than 15, both the performance and the yield of the resulting modified phenolic resin hardly change, so that it is wasted.

Specific examples of the acid catalyst include Bronsted acids and Lewis acids, but Bronsted acids are preferred. As the Bronsted acid, p-toluenesulfonic acid, hydrochloric acid, sulfuric acid, formic acid and the like can be used, but p-toluenesulfonic acid and hydrochloric acid are particularly preferable. The amount of the acid catalyst used is 0.1 to 30% by weight, preferably 1 to 10% by weight, based on the total amount of petroleum heavy oils or pitches and formaldehyde. When the amount of the acid catalyst used is small, the reaction time is prolonged, and when the amount is too large, the reaction speed is not so high, which is disadvantageous in cost.

Examples of phenols include phenol, orthocresol, metacresol, paracresol, xylenol, resorcin, catechol, hydroquinone, bisphenol A, bisphenol F, α-naphthol,
Phenol compounds such as β-naphthol can be used, and these can be used alone or in combination of two or more as raw phenols. Phenol is most suitable. The number of moles of the phenols is from 0.3 to 1 mole per mole of the value calculated from the average molecular weight of the petroleum heavy oils or pitches.
It is preferably 10 mol, more preferably 0.5 to 5 mol. If the addition amount is 0.3 mol or less, the mechanical strength of the finally obtained cured product tends to decrease, which is not preferable. On the other hand, when the amount is more than 10 mol, the modifying effect of the resulting modified phenolic resin is small, which is not preferable.

The reaction for obtaining the modified phenolic resin in the component (B) can be carried out without a solvent or using a solvent. Specific examples of solvents that can be used include aromatic hydrocarbons such as toluene and xylene, ketones such as methyl isobutyl ketone, halogenated aromatic hydrocarbons such as chlorobenzene, and nitrated aromatic hydrocarbons such as nitrobenzene. And nitrated aliphatic hydrocarbons such as nitroethane and nitropropane, and halogenated aliphatic hydrocarbons such as perchrene, trichlene and carbon tetrachloride. After completion of the reaction, it is preferable to perform a neutralization treatment or a water washing treatment to adjust the pH value of the reaction system to 3 to 7, preferably 5 to 7. When performing the neutralization treatment, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkaline earth metal hydroxides such as calcium hydroxide and magnesium hydroxide, ammonia, diethylenetriamine, triethylenetetramine, aniline, and phenylene Organic amines such as diamines can be used as neutralizing agents. In the case of the water washing treatment, it may be carried out according to a conventional method. For example, water in which the neutralizing agent is dissolved may be added to the reaction system, and the separation and extraction operation may be repeated. After the neutralization treatment, when a solvent is used, the solvent is distilled off under heating under reduced pressure and a concentration operation is performed to obtain a desired modified phenol resin.

The modified phenolic resin in the component (B) contains the following components (I) and (II) in the resin skeleton. _{-Ph-CH 2 - ····· (I} ) -PC-CH 2 - ····· (II) wherein, Ph is phenol - indicates Le acids, and the like such as those exemplified above Two or more components (I) using different phenols may be contained in the resin. PC
Represents a condensed polycyclic aromatic hydrocarbon, for example, naphthalene, anthracene, phenanthrene, pyrene, benzanthracene, benzopyrene, etc.
And the like. The resin may contain two or more types of component (II) using different condensed polycyclic aromatic hydrocarbons.

As an example of the above modified phenol resin,
This is disclosed in JP-A-7-252339. This modified phenol resin can be obtained as a PPF resin manufactured by Kashima Oil Co., Ltd.

The properties of the modified phenol resin vary depending on the production conditions, but the modified phenol resin that can be used in the molding material of the present invention is limited. That is, the melt viscosity at 150 ° C. is 5 poise or less and the hydroxyl equivalent is 150 poise.
The following are essential conditions: When the melt viscosity at 150 ° C. exceeds 5 poise, the viscosity of the molding material becomes too high, and when a semiconductor device is produced by molding, molding defects such as unfilling failure and bending of a gold wire are likely to occur. Absent. Further, when the hydroxyl equivalent exceeds 150, although depending on the type of epoxy resin to be combined, the crosslinked density of the cured product is insufficient, so that the hardness at the time of heating becomes low, and the present invention cannot be achieved.

The component (B) used in the present invention comprises:
The component (A) acts as a curing agent for the epoxy resin. The modified phenol resin may be used alone, or another conventionally known curing agent may be used in combination.
As curing agents that can be used in combination, phenol, cresol,
Resorcin, catechol, bisphenol A, phenols such as bisphenol F or α-naphthol, β-naphthol, naphthols such as dihydroxynaphthalene and aldehydes such as formaldehyde and a resin obtained by condensation or cocondensation under an acidic catalyst, Phenol / aralkyl resins, naphthol / aralkyl resins, etc., may be used alone or in combination of two or more. However, in order to effectively exhibit the present invention, the content of the modified phenolic resin should be adjusted to the component (B). Is preferably 50% by weight or more, preferably 70% by weight or more, based on the total amount of the curing agent.

The epoxy resin (A) and the epoxy resin (B)
The equivalent ratio of the curing agent of the component, that is, the ratio of the number of epoxy groups in the epoxy resin / the number of hydroxyl groups in the curing agent is 0.8 to 1.
Setting the value in the range of 2 is an essential condition for achieving the present invention. Outside this range, good moldability cannot be obtained.

Next, the inorganic filler of the component (C) is used for reducing the hygroscopicity, improving the mechanical strength and reducing the linear expansion coefficient. Examples of inorganic fillers that can be used include fused silica, crystalline silica, alumina, zircon, calcium silicate, calcium carbonate, silicon carbide, aluminum nitride, boron nitride, beryllia, zirconia, and other powders, or spherical beads of these. And monocrystalline fibers such as potassium titanate, silicon carbide, silicon nitride and alumina, glass fibers, etc., and fused silica powder is particularly preferred. Also, regarding the shape of the filler, from the viewpoint of fluidity,
A spherical or nearly spherical shape is preferred.

It is an essential condition that the compounding amount of the filler (C) is 80 to 93% by weight based on the whole composition constituting the molding material. If it is less than 80% by weight, the water absorption becomes large, and the reflow resistance is not sufficient. If it is more than 93% by weight, the fluidity of the molding material is insufficient.

The molding material of the present invention includes the above (A) to
A curing accelerator can be used in addition to the component (C).
For example, 1,8-diaza-bicyclo (5,4,0) undecene-7,1,5-diaza-bicyclo (4,3,0)
Tertiary amines such as nonene-5,6-dibutylamino-1,8-diaza-bicyclo (5,4,0) undecene-7, benzyldimethylamine, triethanolamine, dimethylaminoethanol, and tris (dimethylaminomethyl) phenol And derivatives thereof, 2-methylimidazole, 2-phenylimidazole, 2-phenyl-4
-Imidazoles such as methylimidazole, organic phosphines such as tributylphosphine, methyldiphenylphosphine, triphenylphosphine, diphenylphosphine, and phenylphosphine; and phosphines having a π bond such as maleic anhydride, benzoquinone, and diazophenylmethane. Phosphorus compounds having intramolecular polarization obtained by adding a compound, such as tetraphenylphosphonium tetraphenylborate, triphenylphosphine tetraphenylborate, 2-ethyl-4-methylimidazole tetraphenylborate, and N-methylmorpholine tetraphenylborate And tetraphenylboron salts. These may be used alone or in combination of two or more.

Further, other additives include a surface treating agent such as a silane coupling agent, a flame retardant such as a brominated epoxy resin, a nitrogen-containing compound such as antimony trioxide, a phosphate ester and a melamine resin, and a natural wax. A releasing agent such as synthetic wax, oxidized or non-oxidized polyolefin, a coloring agent such as carbon black, a stress relieving agent such as silicone oil or silicone rubber powder, etc. can be used as required.

The molding material in the present invention can be prepared by any method as long as the various raw materials can be uniformly dispersed and mixed. As a general method, the raw materials having a predetermined blending amount are sufficiently mixed by a mixer or the like. After mixing, melt-kneading with a mixing roll, extruder, etc., cooling,
A pulverizing method can be used. It is easy to use if it is tableted with dimensions and weight that match the molding conditions.

For supporting members such as lead frames, wired tape carriers, wiring boards, glass and silicon wafers,
A semiconductor device can be manufactured by mounting a semiconductor element and sealing necessary portions with the molding material of the present invention. As a method of sealing a semiconductor element, a low-pressure transfer molding method is most common, but an injection molding method, a compression molding method, or the like may be used.

EXAMPLES Next, examples of the present invention will be described, but the scope of the present invention is not limited to these examples.

Examples 1 to 9 and Comparative Examples 1 to 10 In addition to the epoxy resins and curing agents shown in Table 1 of FIG. 1 and Table 2 of FIG. 2, 1,8-diazabicyclo (5,4,0 ) Phenol-novolak resin salt of undecene-7 (DBU) (DBU content: 30% by weight), carnauba wax as a releasing agent, carbon black as a coloring agent, 3-glycidoxypropyltrimethoxysilane as a coupling agent, Using spherical fused silica powder having an average particle diameter of 16μ as a filler, Examples 1 to 9 had the composition shown in Table 3 in FIG. 3 and Comparative Examples 1 to 10 had the composition shown in Table 4 in FIG. After mixing with a metal blend, a kneading temperature of 80 to 90 ° C.
Kneading was performed under the conditions of a kneading time of 10 to 12 minutes, and the sheet-like kneaded material was cooled and pulverized to produce molding materials of Examples 1 to 9 and Comparative Examples 1 to 10.

The curing agents 1 to 4 shown in Table 2 of FIG.
Has an average molecular weight of 270 (value by vapor pressure osmosis method), a boiling point of 242 to 467 ° C., and an aromatic hydrocarbon fraction (fa value) of 0.1.
It was prepared using a raw material oil having an aromatic hydrogen content (Ha value) of 0.29, paraformaldehyde, p-toluenesulfonic acid and phenol.

A total of 19 types of molding materials produced were evaluated by the following method. (1) Fluidity (spiral flow: SF) Using a mold for measuring spiral flow according to EMMI-1-66, a mold temperature of 175 ° C and a molding pressure of 70 kg / c.
Molding was performed under the conditions of m ² and a curing time of 90 seconds, and the flow distance was determined. (2) Hot Hardness A disk-shaped molded product having a diameter of 50 mm and a thickness of 3 mm was molded under the conditions of a molding temperature of 175 ° C., a molding pressure of 70 kg / cm ² , and a curing time of 90 seconds, and the molded product hardness immediately after the mold was opened. Was measured using a Shore-D hardness tester. (3) Reflow crack resistance Using each molding material, dimensions 20 × 14 × 2 mm, number of pins 8
QFP (QuadFlatPackage, chip size: 8 × 10 mm) at 175 ° C. for 6 hours
A test package was prepared by post-curing. This package is placed in a thermo-hygrostat at 85 ° C / 85% RH.
After humidification for a certain period of time under the above conditions, the mixture was immediately heated at 215 ° C./90 seconds using a vapor phase reflow apparatus. After cooling to room temperature, the presence or absence of cracks was observed using a stereo microscope or an ultrasonic probe.

The evaluation results are shown in Table 5 of FIG. 5 and Table 6 of FIG. In Comparative Example 1 in which the modified phenol resin in the component (B) in the present invention was not contained, the reflow resistance was poor, and (A)
In Comparative Example 4 which does not contain the epoxy resin as a component (only contains an epoxy resin having a small number of epoxy groups), the moldability (hardness when heated) is inferior. Comparative Example 2, which does not contain both,
3 also has a low hardness when heated. The properties of the modified phenolic resin in the component (B) do not meet the target values even in Comparative Examples in which the properties of the modified phenolic resin are outside the limits of the present invention. That is, the hydroxyl equivalent is 150
In Comparative Example 5, which exceeds 100, the fluidity and the hardness at the time of heating are poor, and in Comparative Example 6, which has a high melt viscosity, the fluidity and the reflow resistance are inferior. Comparative Example 7, in which the content of the component (C) was low,
Sample No. 8 has poor reflow resistance, and Comparative Examples 9 and 10 in which the equivalent ratio of component (A) to component (B) is not in the range of 0.8 to 1.2 have low hot hardness.

On the other hand, all the components (A) to (C) are contained, the equivalent ratio of the components (A) and (B), the properties of the modified phenolic resin in the component (B), and the content of the component (C). Examples 1 to 9 in which the content satisfies the limitations of the present invention are all excellent in fluidity, hardness at hot time, and reflow crack resistance.

[0033]

The epoxy resin molding material for semiconductor encapsulation obtained according to the present invention is excellent in moldability and thus contributes to high productivity of semiconductors. As shown in the examples, since it has excellent reflow crack resistance, its industrial value is great.

[Brief description of the drawings]

FIG. 1 is a table showing contents of an epoxy resin used for a molding material.

FIG. 2 is a table showing contents of a curing agent used for a molding material.

FIG. 3 is a table showing the composition of Examples.

FIG. 4 is a table showing a composition of a comparative example.

FIG. 5 is a table showing characteristics (evaluation results) of molding materials of Examples.

FIG. 6 is a table showing characteristics (evaluation results) of molding materials of Comparative Examples.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 23/31

Claims (2)

[Claims] (1) The average number of epoxy groups in one molecule (A) is 2.
(B) a curing agent containing a modified phenol resin obtained by reacting a phenol, a condensed polycyclic aromatic hydrocarbon and a formaldehyde source, and (C) an inorganic filler as an essential component. When the number of epoxy groups in the component (A) is X and the number of hydroxyl groups in the component (B) is Y, X / Y = 0.8 to 1.2, and the component (B) The modified phenolic resin has a melt viscosity at 150 ° C. of 5 poise or less and a hydroxyl equivalent of 150 or less, and the content of the component (C) is 80 to 93% by weight based on the whole molding material. Characteristic epoxy resin molding material for semiconductor encapsulation. 2. A semiconductor device sealed with a cured product of the molding material according to claim 1.