KR101127933B1 - Epoxy resin composition having excellent attachment property and mold-contamination resistance for environment friendly sealing semiconductor devices - Google Patents

Abstract

The present invention is an environmentally friendly semiconductor encapsulation epoxy having excellent adhesion and solder reflow properties with lead frames such as preplated Ni-Pd, Ni-Pd-Au, Ag, and Ni. In providing a resin composition, the epoxy resin composition includes an epoxy resin, a phenol resin, a curing accelerator, an inorganic filler, a curing accelerator, and an acid anhydride having a carboxyl group, and additionally, zinc borate, hydrotalcite ) Or a combination of both. Moreover, this invention provides the semiconductor device using the said epoxy resin composition.

Description

EPOXY RESIN COMPOSITION HAVING EXCELLENT ATTACHMENT PROPERTY AND MOLD-CONTAMINATION RESISTANCE FOR ENVIRONMENT FRIENDLY SEALING SEMICONDUCTOR DEVICES}

The present invention is a pre-plated (Ni-Pd, Ni-Pd-Au, Ag, Ni) lead frame by applying an epoxy resin composition for semiconductor element encapsulation, specifically, a coupling agent semifinished product prepared by Process 1 according to the present invention. The present invention relates to an epoxy resin composition for environmentally friendly semiconductor device encapsulation, which can ensure high reliability even under high temperature solder reflow under lead-free conditions by maintaining high adhesion to the resin.

Background Art In recent years, semiconductor devices have become a mainstream technology for sealing using epoxy resin compositions that are excellent in productivity, cost, and reliability. However, in this technology, when assembling the semiconductor device according to the surface mount technique, the process temperature rises rapidly to a high temperature of 200 ° C. or higher in the solder reflow process, and thus, the moisture absorbed explosively vaporizes to generate stress. Stress causes peeling at the interface between the semiconductor element, lead frame, various preplated joints on the inner lead and the epoxy resin composition, which has a problem of deteriorating the reliability of the assembled semiconductor device. .

In addition, in many countries, regulations on environmentally hazardous substances such as the Restriction of Hazardous Substances Directive (RoHs) have been implemented, leading to the use of Pb-free solders in the joining process of electrical and electronic devices. ) Is mandatory. For example, Sn-Pb plating is gradually being replaced by plating using lead-free solder. Conventional methods for lead-free Sn-Pb plating can be roughly divided into pure Sn plating and Ni-Pd pre-plating. Ni-Pd preplating (also referred to as 'PPF') has been proposed as a solution to overcome the above problems. However, since the Ni-Pd preplating has a significantly lower interface adhesion force with the epoxy resin composition than the conventional Alloy 42 and the copper lead frame, the Ni-Pd preplating still has problems of reliability deterioration such as peeling after post-curing and reliability test.

In order to improve the reliability deterioration problem after solder reflow under the lead-free condition, the amount of inorganic fillers in the epoxy resin composition is increased to achieve low hygroscopicity, high strength, and low heat retention, thereby improving solder reflow resistance. The technique of making high fluidization by the said low melt viscosity at the time of shaping | molding by using resin of melt viscosity was common.

However, in the reliability of the semiconductor device after bonding, the adhesive force at the interface between the cured product of the resin composition and the semiconductor element lead frame existing in the semiconductor device and the substrate serves as an important factor. That is, when the adhesive force at the interface is weak, peeling occurs at the interface, and such peeling causes cracking in the semiconductor device, thereby lowering the reliability of the semiconductor device.

Conventionally, silane coupling agents such as gamma methacryloxy propyltrimethoxy silane, amino silane, mercapto silane, or the like are used to improve solder reflow resistance and to secure reliability in lead frames such as Cu, Ag, and Ni. It is known that the adhesion in the adhesive layer between the lead frame and the EMC is increased when the mixture thereof is added to the epoxy resin composition in liquid form.

However, in order to cope with the reflow of solder, which has been strengthened by the recent rise of reflow temperature during mounting and the appearance of pre-plated lead frames such as Ni-Pd and Ni-Pd-Au for securing reliability in lead-free solder, Techniques such as increasing the amount of coupling agent added or adding an adhesion enhancer such as an indene oligomer have been used for the purpose of improving the adhesion effect with the resin.

However, the above technique can improve adhesion to pre-plated lead frames such as Ni-Pd and Ni-Pd-Au, but increases the bleed flush by the liquid coupling agent after molding the epoxy resin composition. In addition, there is a problem in that the storage property is drastically deteriorated due to the contamination of the mold and the reaction of the coupling agent during the storage of the epoxy resin composition at room temperature, and also in the case of using an adhesion enhancer such as an indene oligomer, there is a slight problem of improving adhesion. .

Accordingly, the present inventors have intensively researched to overcome the problems of the prior art, and as a result, when encapsulating a semiconductor device using the epoxy resin composition according to the present invention, mold contamination prevention and storage properties are not only improved, but Ni- By exhibiting excellent adhesion with pre-plated lead frames such as Pd and Ni-Pd-Au, it has been found that a semiconductor device excellent in reliability after solder reflow can be assembled, and the present invention has been completed.

The present invention relates to (A) an epoxy resin, (B) a phenol resin, (C) a curing accelerator, (D) an inorganic filler, and (E) (a) the reactant I according to the following step 1, (b) the following step 1 Reactant II or (c) reactant III according to the following process 1, wherein the content of component (E) is 0.02 to 5% by weight based on the total amount of the total epoxy resin composition. To provide.

<Step 1>

① After the phenol resin is melted in the reactor at 110 to 140 ° C., 10 parts by weight of epoxy silane and 1 part by weight of a curing accelerator are added to 100 parts by weight of the phenol resin;

② collecting the reactants I, II and III after 2, 6 and 8 hours from the start of the reaction; And

Determining the reaction rate for reactants I, II and III collected from step ② as the ring opening rate of the epoxy ring of the epoxy silane using nuclear magnetic resonance (hereinafter also referred to as 'NMR')

The reaction rate for each reaction time in step 1 is shown in Table 1 below.

One aspect of the present invention is to provide an epoxy resin composition in which reactant II (component (E) (b)) according to the above step 1 has a reaction rate of 20% or more and 40% or less of phenol and epoxy silane.

In another embodiment of the present invention, the epoxy resin composition may further include zinc borate salt of Formula 1, hydrotalcite of Formula 2, or a combination thereof as (H) a non-halogen-based flame retardant. Preferably, the non-halogen flame retardant is a combination of both the zinc borate salt and hydrotalcite.

A further aspect of the present invention is to provide a semiconductor device in which a semiconductor element is sealed and assembled using the epoxy resin composition.

When encapsulating a semiconductor device using the epoxy resin composition of the present invention, it is advantageous because the incidence of package peeling can be significantly reduced to improve the reliability of the encapsulated semiconductor device and the semiconductor device provided with the device. In addition, the epoxy resin composition of the present invention has an advantage in terms of environmental aspects in that it is a lead-free solder that is excellent in storage properties and mold contamination prevention capabilities and does not contain lead harmful to the environment.

Figure 1 shows the adhesion strength evaluation test process of the specimen prepared according to the present invention.

Hereinafter, the present invention is described in more detail in terms of the components of the composition.

(A) epoxy resin

In the present invention, the epoxy resin is a bisphenol A type epoxy resin, an o-cresol novolak type epoxy resin, a naphthol novolak type epoxy resin, a phenol aralkyl type epoxy resin, a dicyclopentadiene modified phenol type epoxy resin, a biphenyl type epoxy Resins, stilbene type epoxy resins, and the like, and these may be used alone or as a combination of two or more. In consideration of the moisture resistance reliability as the resin composition for environmentally friendly semiconductor encapsulation, the smaller the content of Na ⁺ ions or Cl ^- ions, which are ionic impurities, is preferable, and the epoxy equivalent is preferably 100 to 500 g / eq. In the case where the equivalent is more than 500g / eq, the adhesion may be lowered due to the decrease in flowability, when using less than 100g / eq it is difficult to have a proper Tg value.

(B) phenolic resin

In the present invention, the phenol resin may include a phenol novolak resin, a phenol aralkyl resin, a terpene modified phenol resin, a dicyclopentadiene modified phenol resin, and the like, and these may be used alone or as a combination of two or more. The equivalent of hydroxyl group is preferably 90 to 250g / eq in consideration of the curable side, and when the equivalent of hydroxyl group is used more than 250g / eq, the adhesiveness may be lowered due to the deterioration of flowability, using less than 90g / eq In this case, it is difficult to have an appropriate Tg value.

(C) curing accelerator

In this invention, what is necessary is just to accelerate reaction of an epoxy group and phenolic hydroxyl group as a hardening accelerator, and what is generally used in the field of sealing materials can be used. Diazabicyclo alkenes and derivatives thereof such as 1,8-diazabicyclo (5,4,0) undecene-7; Amine compounds such as tributylamine and benzyldimethylamine; 2-methylimidazole compound, tetraphenyl phosphonium tetraphenyl borate, tetraphenyl phosphonium tetranaphthoic acid borate, tetraphenyl phosphonium tetranaphthoic oxy borate, tetraphenyl phosphonium tetranaphthyloxy borate Tetra substituted phosphonium tetra tetra borate etc., etc. are mentioned, These can be used individually or as a combination of 2 or more. The amount of the catalyst is suitably 0.1 to 5% by weight relative to the total amount of the total epoxy resin composition, when the amount of the catalyst is used more than 5% by weight may cause a decrease in adhesion due to the lack of flow, less than 0.1% by weight In the case of using the same, proper workability cannot be secured due to an increase in gelation time.

(D) inorganic filler

In the present invention, as the inorganic filler, fused silica, spherical silica, crystalline silica, alumina, silicon nitride, aluminum nitride may be used. The particle size of the inorganic filler is preferably a maximum particle size of 150 um or less in consideration of the filling ability to the mold. In addition, the blending amount of the filler is preferably 80 to 94% by weight relative to the total amount of the total epoxy resin composition, when the blending amount is less than 80% by weight, the moisture absorption amount in the cured product of the epoxy resin composition increases, and the increase in the moisture absorption amount decreases the strength. This may lower the adhesion after solder reflow, and if it exceeds 94% by weight, it is not preferable because it may cause moldability defect by causing fluidity loss.

(E) the reactants according to process 1

The reactant in step 1 according to the present invention is the adhesion between the cured product of the resin composition and the lead frame according to the reaction rate of the epoxy silane, especially when the reaction rate of the epoxy silane and phenol resin is 20% or more and 40% or less It exhibits excellent adhesion, and when the viscosity is 7% or less, there is no effect of increasing the adhesiveness, and when 60% or more, there is a problem in that the adhesion of the epoxy resin composition is lowered due to an increase in the viscosity of the reactants.

The phenol resin used in step 1 refers to a monomer, oligomer, or polymer in general having two or more phenolic hydroxyl groups per molecule, and its molecular weight and molecular structure are not particularly limited. Examples of the phenol resins include phenol novolac resins, phenol aralkyl resins, terpene-modified phenol resins, dicyclopentadiene-modified phenol resins, and the like. In the embodiment of the present invention, an aralkyl resin was used as the phenol resin.

The kind of epoxy silane in the said process 1 is not specifically limited. However, the difference in the reaction rate between the epoxy silane and the phenol resin occurs depending on the molecular weight of the epoxy silane, which may result in a difference in adhesion. In the Example of this invention, (gamma)-methacryloxy propyl trimethoxy silane was used as an epoxy silane.

The kind in particular of the hardening accelerator in the said process 1 is not restrict | limited. However, the reaction rate may vary depending on the type of curing accelerator. Triphenyl phosphonium was used as a curing accelerator in the embodiment of the present invention.

The amount of the reactant according to Step 1 is preferably 0.02 to 5% by weight based on the total amount of the total epoxy resin composition. When the amount of the reactants is less than 0.02% by weight, poor reliability may occur due to a decrease in adhesion, and when the amount of the reactants exceeds 5% by weight, poor workability may occur due to an increase in viscosity.

(F) Flame retardant

In the present invention, as the flame retardant, zinc borate salt of Chemical Formula 2 and hydrotalcite of Chemical Formula 3 are used alone or as a combination of both. The zinc borate has a melting point of 260 ° C. and excellent heat resistance, electrical properties, and moisture resistance. The zinc borate exhibits endothermic phenomenon as a dehydration reaction occurs at a high temperature, and exhibits a high flame retardant effect by an endothermic amount of 530 J / g. Zinc borate used in the present invention is characterized by high purity by lowering the concentration of Na impurities to 10ppm or less, and also the decomposition of the combustion products to form a stable carbon layer (Char) has excellent flame retardant effect compared to the conventional halogen-based flame retardant Exert. In the case of including zinc borate and hydrotalcite at the same time as the flame retardant is excellent in the flame retardant effect can be satisfied even at low silica content.

The amount of the flame retardant is preferably 0.5 to 5% by weight based on the total amount of the total epoxy resin composition. When the amount of the flame retardant is less than 0.5% by weight, it is difficult to obtain a flame retardant effect, and when the amount of the flame retardant is greater than 5% by weight, there is a problem in that the flow characteristics are deteriorated and the moldability is deteriorated.

Although the epoxy resin composition of this invention contains components (A)-(E) as an essential component, Silane coupling agents, such as an epoxy silane, a mercapto silane, an amino silane, an alkyl silane, a ureide silane, a vinyl silane; Titanate coupling agents; Aluminum / zirconium coupling agents; Carbon black; Coloring agents such as bengala; Natural waxes such as carnauba wax; Synthetic waxes such as polyethylene wax; Higher fatty acids such as stearic acid or zinc stearate and metal salts thereof; Mold release agents such as paraffin; Low stress components such as silicone oil and silicone rubber; Flame retardants such as brominated epoxy resins, antimony trioxide, aluminum hydroxide, magnesium hydroxide, zinc borate, zinc molybdate, phosphazene; Various additives, such as inorganic ion exchangers, such as a bismuth oxide oxide, can also be mix | blended suitably and used.

In the epoxy resin composition of the present invention, the components (A) to (F) and other additives are uniformly mixed at room temperature using a mixer or the like, followed by a heating roll or a kneader or an extruder. It can be melt-kneaded with the cooling, cooled and pulverized before production.

In order to seal a semiconductor element using the epoxy resin composition of this invention and to manufacture a semiconductor device, what is necessary is just to harden | cure by the shaping | molding methods, such as transfer molding, compression molding, injection molding, etc. .

Example

Hereinafter, the present invention will be described in more detail by the following examples, but the present invention is not limited by these examples. The blending ratio is in weight parts.

Evaluation

(One) Viscosity

The viscosity was measured using a capillary tube visometer at a heating temperature of 175 ° C., a piston pressure of 60 kgf, a capillary diameter of 0.5 mm, a capillary length of 10 mm, and a preheating time of 3 seconds. Using a tableting machine, a density of 1.8 g / cm ³ and a height of 20 mm were manufactured. The measurement result recorded the lowest viscosity as a measurement result on a time-viscosity graph.

(2) Bleed  Flush ( bleed flush )

The measurement of the bleed flush was judged as defective if the bleed flush exceeded the package damper line after forming 160 pLQFP (24 mm X 24 mm X 1.4 mm thick) at a mold temperature of 175 ° C., an injection pressure of 9.3 Mpa, and a curing time of 60 seconds.

(3) my solder Reflowability

Using a transfer molding machine, molding 160pLQFP (24mm X 24mm X 1.4mm thickness) at mold temperature 175 ℃, injection pressure 9.3Mpa, curing time 60sec, postcure 4 hours at 175 ℃, 85 ℃, relative humidity 85% The solder reflow resistance was investigated by standing for 168 hours in the constant temperature and humidity bath of (I) and IR reflow treatment (260 ° C, 3 times). It was judged as pass that there was no crack and peeling after a process. (N = 36)

(4) wire  Sweep ( wire sweep )

Using a transfer molding machine, 160pLQFP (24mm X 24mm X 1.4mm thickness) equipped with 10mil Au gold wire at mold temperature of 175 ℃, injection pressure of 9.3Mpa and curing time of 60 seconds was determined using X-ray. When the length of the arc out of the distance between the straight lines in the silver-wire bonding post became 10% or more, it was judged as defective. (N = 10)

(5) adhesion strength

As shown in FIG. 1, 10 specimens were molded per level using a transfer molding machine at a mold temperature of 175 ° C., an injection pressure of 9.3 Mpa, and a curing time of 60 seconds. As the lead frame, an Ag plated lead frame (lead frame A) and a Ni-Pd-Au preplated lead frame (lead frame B) were used.

(6) Zhejiang

The shelf life was compared with the viscosity measured immediately after preparation and the increase rate of the viscosity value after standing at 25 ° C. for 72 hours.

(7) mold Pollutant

Mold contamination has problems in continuous workability such as mold sticking and void formation when continuously molding 160pLQFP (24mm X 24mm X 1.4mm thick) at mold temperature 175 ℃, injection pressure 9.3Mpa, curing time 60sec. The time point to cause was set as the cleaning cycle of the mold.

Example  One

5.2 weight% of biphenyl-type epoxy resin (made by Japan epoxy resin, YX-4000HK, melting | fusing point 105 degreeC; epoxy equivalent 191), phenol aralkyl resin (made by Meiwa Corporation, MEH-7800-4S, softening point 61 degreeC, equivalent 169) ) 4.8 wt%, triphenyl phosphine 0.2 wt%, spherical silica (average particle size 15 um) 87.0 wt%, carnava wax 0.2 wt%, 1.0 wt% reactant II according to process 1, 1 wt% zinc borate, hydrotal 1% by weight of the site, 0.1% by weight of bismuth oxide hydrate and 0.1% by weight of carbon black were mixed at room temperature in a mixer, dissolved and kneaded in a heating roll at 80 to 100 ° C, and then cooled and pulverized to obtain an epoxy resin composition. The evaluation results are shown in Table 2 below.

Example  2 and 3, and Comparative example  1 to 2

According to the mixing | blending ratio of following Table 2, the epoxy resin composition was produced like Example 1, and it evaluated by the same method. The evaluation results are shown in Table 2 below.

In Examples 2 and 3 other than Example 1 and Comparative Examples 1-2, the following components were used.

o-cresol novolac type epoxy resin (softening point 55 ° C, epoxy equivalent weight 196)

Phenolic novolac resin (softening point 81 ° C, hydroxyl equivalent 105)

Epoxy coupling agent (Tosoh Corporation make, S-510, molecular weight 278.4)

In Examples 1 to 3 using the epoxy resin composition of the present invention, the incidence of package peeling was remarkably improved as compared with Comparative Examples 1 to 2 to which the reactant I according to Step 1 was applied. In addition, the storage properties of Examples 1 to 3 to which the reactants II and III according to the process 1 were applied were 5 to 7% of the storage stability of Comparative Examples 1 to 2, and the mold contamination was significantly improved in Example 1 It can be seen that to 3 to extend from at least 1 day to a maximum of 3 days compared to Comparative Examples 1 to 2.

Claims (6)

(A) an epoxy resin, (B) a phenolic resin, (C) a curing accelerator, (D) an inorganic filler, and (E) (a) a reactant I according to step 1, (b) a reactant II according to step 1, or (c) Epoxy resin composition for encapsulating an environmentally-friendly semiconductor device, comprising reactant III according to Step 1, wherein the content of component (E) is 0.02 to 5% by weight based on the total amount of the total epoxy resin composition:
<Step 1>
(1) adding phenol resin to the reactor at 110 to 140 ° C., and then adding 10 parts by weight of epoxy silane and 1 part by weight of curing accelerator to 100 parts by weight of phenol resin;
② collecting the reactants I, II and III after 2, 6 and 8 hours from the start of the reaction; And
(3) Determining the reaction rate for reactants I, II and III collected from step ② as the ring opening rate of epoxy ring of epoxy silane using nuclear magnetic resonance method The method of claim 1,
Epoxy resin composition, characterized in that the reaction rate of reactant II according to step 1 is 20% or more and 40% or less. The method of claim 1,
(H) an epoxy resin composition further comprising zinc borate salt of Formula 1, hydrotalcite of Formula 2, or a combination thereof as a non-halogen flame retardant:
Formula 1

Formula 2

The method of claim 3, wherein
Epoxy resin composition, characterized in that the non-halogen flame retardant is a combination of the zinc borate and hydrotalcite. The semiconductor element sealed using the epoxy resin composition of any one of Claims 1-4.  A semiconductor device comprising a semiconductor element sealed using the epoxy resin composition according to any one of claims 1 to 4.

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