JP3396363B2 - Resin composition for ball grid array - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition for a ball grid array (hereinafter referred to as "BGA"), and more particularly to a resin composition capable of obtaining a package having an extremely small warp amount.

[0002]

2. Description of the Related Art Resin compositions for semiconductors have been developed and produced in order to protect IC bodies from mechanical and chemical effects. However, recently, due to the improved chip reliability,
The purpose of sealing is changing. For example, improvements in heat dissipation and electrical characteristics have been highlighted as required characteristics. Furthermore, the development of a system that can be produced and mounted at a low price has been actively promoted, and BGA has been created as one of the new packages. Since the BGA has a structure in which an IC chip is directly mounted on a substrate and is covered with a resin composition, this bimetal-like structure has a drawback that warpage occurs due to temperature. Until now, the characteristics of the resin composition capable of reducing the warp amount in all temperature ranges (-65 ° C to 250 ° C) have not been found.

[0003]

SUMMARY OF THE INVENTION The present invention is directed to the entire temperature range in which a BGA type semiconductor device is used, that is, -65 ° C to 2 ° C.
The present invention provides the characteristics of a resin composition capable of obtaining a package having an extremely small amount of warpage at 50 ° C.

[0004]

DISCLOSURE OF THE INVENTION The present invention is a resin containing an epoxy resin, a phenol resin curing agent, 78 to 93% by weight of an inorganic filler with respect to 100% by weight of the total composition, and a curing accelerator as essential components. A composition, wherein a cured product of the resin composition has characteristics of a curing shrinkage of 0.15% or less and a thermal expansion coefficient of 0.8 × 10 ^{−5 to} 1.5 × 10 ⁻⁵ / ° C. at room temperature. A resin composition for a ball grid array, which preferably has a glass transition temperature of 180 ° C. or higher in a cured product in addition to the above characteristics. More preferably, the epoxy resin is the following formula 1 and the phenol resin curing agent is the following formula 2
The resin composition for a ball grid array shown in FIG.

[Chemical 3]

[Chemical 4]

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The epoxy resin used in the present invention is
Examples thereof include orthocresol novolac type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, triphenol type epoxy resin, naphthalene type epoxy resin, biphenyl type epoxy resin, and the like. Mold epoxy resins are preferred. Since the epoxy resin of Formula 1 has a rigid main chain and no flexibility, the main chain does not bend even when it reacts with the phenol resin. Therefore, the free volume is not collapsed during the curing reaction, so that the curing shrinkage rate is small. Note that the biphenyl structure is also rigid, but since it is planar, the molecules are stacked and the free volume decreases during curing, so the curing shrinkage is large. Furthermore, it is considered that the triphenolmethane type epoxy resin has a high glass transition temperature (hereinafter, referred to as Tg) due to this rigidity, and has a structure that is highly effective in reducing the warpage of BGA. The functional group R in Formula 1 is a hydrogen, methyl or t-butyl group. These may be the same or different. The epoxy resin used in the present invention is not particularly limited in terms of average molecular weight and epoxy equivalent, but it is desirable that the amount of ionic impurities is as small as possible in order to improve reliability.

The phenol resin curing agent used in the present invention includes, for example, phenol novolac resin, paraxylylene-modified phenol novolac resin, triphenol methane type phenol novolac resin, bisphenol A, and the like. Phenolmethane type phenol novolac is preferred. Similar to the triphenolmethane type epoxy resin of Formula 1, the main chain is rigid and has no flexibility, so that the main chain does not bend even when the curing reaction occurs.
Therefore, the free volume does not collapse during the curing reaction, so the curing shrinkage is low. In particular, it was found that the curing shrinkage becomes almost zero when used in combination with a triphenol methane type epoxy resin. Furthermore, triphenolmethane type phenol novolac resin has a high Tg because of this rigidity,
It is considered that the structure is highly effective in reducing the warpage of BGA. The functional group R in formula 2 is either hydrogen, a methyl or a methoxy group. These may be the same or different. Phenolic resin curing agent used in the present invention,
The molecular weight and the hydroxyl equivalent are not particularly limited, but it is desirable that the ionic impurities be as low as possible from the viewpoint of improving reliability.

Examples of the inorganic filler used in the present invention include fused silica powder, spherical silica powder, crystalline silica powder, secondary agglomerated silica powder and alumina. Especially the cost,
From the viewpoint of reliability and flowability, spherical silica powder is preferably used. The inorganic filler may be surface-treated in advance with a silane coupling agent, a titanate coupling agent, or another surface treatment agent. The blending amount of the inorganic filler in the present invention is preferably 78 to 93% by weight. If it is less than 78% by weight, the coefficient of thermal expansion becomes 1.5 × 10 ⁻⁵ / ° C. or more, and the warpage of BGA becomes large. If it exceeds 93% by weight, the fluidity is lowered and molding cannot be performed. The average particle size of the inorganic filler, the maximum particle size,
There is no particular limitation on the particle size distribution.

The curing accelerator used in the present invention is, for example, triphenylphosphine, tetraphenylphosphine.
Tetraborate, tetraphenylphosphine / tetranaphthoic acid borate, tetraphenylphosphine / tetrabenzoic acid borate, triphenylphosphine / trihydroborate, 1,8-diazabicyclo (5,4,0)
Any material that promotes a chemical reaction between an epoxy group such as undecene-7 and a phenolic hydroxyl group may be used.

Next, the cause of the warp of the BGA will be described. It is well known that the BGA has a bimetal structure with the circuit board, and thus warps due to a difference in heat shrinkage ratio. Therefore, the degree of shrinkage of various base materials constituting the BGA when cooled from 175 ° C. to 25 ° C. will be roughly estimated and considered. Here, 175 ° C. is a temperature at which BGA is generally molded. The base material that constitutes the BGA is mainly a circuit board, an IC chip, and a resin composition. Of these, the IC chip is 2 times the area of the circuit board.
It is as small as 0 to 50% and does not become the main factor of warpage.
Since the warpage is considered to be caused by the mismatch between the shrinkage ratios of the circuit board and the resin composition, the shrinkage ratios of the two were compared and discussed. However, since the encapsulating resin composition is molded at 175 ° C., it is not possible to consider shrinkage only by the heat shrinkage rate. The total shrinkage rate will be roughly estimated by taking into consideration the hardening shrinkage as the shrinkage caused by the warpage.

Circuit board using bismaleimide triazine resin: coefficient of thermal expansion at room temperature is 1.3 × 10 ⁻⁵
/ ° C, the heat shrinkage rate when cooled from 175 ° C to 25 ° C is 1.3 × 10 ^-5 / ° C × (175-2
5) C. × 100 = 0.195%, which is about 0.2%. Resin composition: Thermal expansion coefficient at room temperature is 1.3 × 1
^Assuming that 0-5 is the same as the thermal expansion coefficient of the circuit board, 175 ° C
The heat shrinkage rate when cooled from 25 to 25 ° C is 1.3 x 10
^{-5 /} ° C x (175-25) ° C x 100 = 0.195%
Then, it becomes about 0.2%. Furthermore, since the general cure shrinkage rate is 0.3%, the total shrinkage rate related to warpage is: total shrinkage rate = cure shrinkage rate + heat shrinkage rate = 0.3
+ 0.2 = 0.5%, which is about 0.5%. Here, the total shrinkage ratio is the sum of the curing shrinkage ratio and the heat shrinkage ratio, as shown in FIG. The curing shrinkage refers to the volume reduction that occurs when the epoxy resin / phenolic resin curing agent in the resin composition at the molding temperature gels from a liquid state to a solid state. The heat shrinkage of the circuit board is 0.2%,
The total shrinkage ratio of the resin composition is 0.5%, and the difference is large. Therefore, even if the BGA is integrally molded at 175 ° C. using the conventional resin composition, the BGA is largely warped.

The shrinkage ratio of the resin composition that minimizes the amount of warp in each temperature range will be considered. First, the total shrinkage rate of the resin composition needs to be 0.2% like the circuit board. Figure 1 shows the correlation between the total shrinkage and the amount of warpage at room temperature. As discussed above, the warpage becomes smaller as the total shrinkage ratio approaches 0.2%. As described above, the total shrinkage is the sum of cure shrinkage and heat shrinkage. Reduce warpage, that is, bring the total shrinkage rate close to 0.2% (in case of room temperature warpage)
The curing shrinkage rate and the heat shrinkage rate necessary for that are considered. Consideration on curing shrinkage A general resin composition shrinks 0.3% immediately after molding,
Here, a warp has already occurred with the circuit board. BGA
It is desirable that the curing shrinkage rate of the resin composition for use is 0%, that is, it is desirable that the curing shrinkage does not occur. However, since the epoxy resin and the phenol resin curing agent always undergo the curing shrinkage due to their chemical structure, a resin composition having a curing shrinkage as small as possible should be used. desired. In the study by the present inventor, it has been confirmed that if the curing shrinkage ratio is 0.15% or less, there is no serious problem in practical use. However, in the case of a resin composition having a curing shrinkage ratio exceeding that, it is 150 to 210 ° C. It is known that the problem of warpage occurs at high temperatures.

The cure shrinkage is calculated by the following formula because the total shrinkage is the sum of the cure shrinkage and the heat shrinkage as described above. Curing shrinkage ratio = total shrinkage ratio−heat shrinkage ratio Equation 3 The total shrinkage ratio is measured by heating a molding die of a disc of 50 to 100 mm to 175 ° C. When heated, the inner diameter of the mold is measured with a precision caliper such as a digital caliper. The value at this time is r ₁ (mm). 17 using this mold
A molded product of the resin composition is prepared at 5 ° C. and an injection pressure of 70 kgf / cm ² for 2 minutes. The obtained molded product is post-cured, treated at 175 ° C. for 8 hours, and then the external shape of the molded product when returned to room temperature is measured. The value at this time is r
₂ (mm). The total shrinkage rate is calculated by the following formula. Total shrinkage (%) = [(r ₁ −r ₂ ) / r ₁ ] × 100 Thermal shrinkage is 175 ° C., injection pressure 70 kgf / cm ² ,
A molded product of the resin composition is produced in 2 minutes, and the thermal expansion coefficient of the molded product that has been heat-treated at 175 ° C. for 8 hours is measured using TMA (thermo-mechanical analysis). The heating rate is 10 ° C./min. After the measurement, the coefficient of thermal expansion at 25 ° C. to 175 ° C. is calculated and treated as the coefficient of thermal contraction. However, if the curing shrinkage rate is 0.15% or less, BG in all temperature ranges
Although the amount of warpage of A can be considerably suppressed, this property alone is insufficient.

Consideration on Thermal Shrinkage Rate Since the thermal expansion coefficient of the circuit board is about 1.3 × 10 ⁻⁵ / ° C., the thermal expansion coefficient of the cured product of the resin composition at room temperature is ideally a circuit. Same as the substrate 1.3 × 10 ^-5 / ° C
Is preferably 0.8 × 10 ^{-5 to} 1.5 × 1
There is no problem if it is 0 ^-5 / ° C. However, 0.8 × 10 ^-5 /
If the temperature is lower than 0 ° C, the BGA largely warps upward near room temperature, and conversely, if it exceeds 1.5 × 10 ^-5 / ° C, the BGA largely warps downward near room temperature. The thermal expansion coefficient was 175 ° C., the injection pressure was 70 kgf / cm ² , a molded product of the resin composition was prepared for 2 minutes, and the molded product was heat treated at 175 ° C. for 8 hours. Measure in minutes. The coefficient of thermal expansion is calculated as the coefficient of thermal expansion in the range of 25 to 60 ° C., and this is taken as the coefficient of thermal expansion at room temperature. Curing shrinkage of the cured product of the resin composition is 0.15% or less, and thermal expansion coefficient at room temperature is 0.8 × 10 ^{−5 to} 1.5 × 10.
^{At -5} / ° C, the physical properties of the ball grid array resin composition are almost satisfied.

Further, it is preferable that Tg is relatively high. In the temperature range of Tg or higher, the resin composition is in a rubber state and the coefficient of thermal expansion is several times that at room temperature. If the resin composition is already in the rubber state at the molding temperature of 175 ° C., the warp amount of BGA in the normal temperature range becomes large. Therefore, Tg is preferably 180 ° C. or higher. Tg is 1
A molded product of the resin composition is produced at 75 ° C. and an injection pressure of 70 kgf / cm ² for 2 minutes, and the molded product subjected to heat treatment at 175 ° C. for 8 hours is measured with TMA at a temperature rising rate of 10 ° C./min. . The temperature at the intersection of the tangent line of the TMA curve at 60 ° C and the tangent line at 240 ° C is defined as Tg.

The composition of the present invention contains an epoxy resin, a phenol resin curing agent, an inorganic filler and a curing accelerator, and if necessary, a coloring agent such as carbon black, a brominated epoxy resin, an antimony trioxide or the like. A flame retardant, silicone oil, silicone rubber, a low stress component such as various rubber components, a silane coupling agent and the like can be added. The resin composition of the present invention is an epoxy resin, a phenol resin curing agent, an inorganic filler, a curing accelerator, and other additives are mixed at room temperature with a mixer, kneaded with a general kneader such as a roll or an extruder, and cooled. It can be pulverized afterwards to obtain a molding material.

The present invention will be specifically described below with reference to examples. << Example 1 >> Epoxy resin A 11.1 parts by weight Phenolic resin curing agent A 5.3 parts by weight Spherical silica (average particle size 15 μm) 80.3 parts by weight Epoxy silane coupling agent 0.5 parts by weight Carbon black 0. 3 parts by weight Carnauba wax 0.3 parts by weight Brominated phenol novolac type epoxy resin 1.0 parts by weight Antimony trioxide 1.0 parts by weight 1,8-diazabicyclo (5,4,0) undecene-7 (DBU) 0. 2 parts by weight were mixed at room temperature with a mixer, kneaded with a twin-screw roll at 100 ° C., cooled and pulverized to obtain a molding material. The curing shrinkage rate, the thermal expansion coefficient at room temperature, Tg, and BGA warpage of the obtained molding material were evaluated, and the results are shown in Table 1.

Evaluation method-Curing shrinkage rate: The curing shrinkage rate is calculated by the above equation 3 from the total shrinkage rate and the thermal shrinkage rate. -Temperature expansion coefficient at room temperature: determined by the method described above. Unit is 1
0 ^-5 / ° C.. -Tg: Determined by the method described above. The unit is ° C. -Amount of warpage of BGA: A molded product shown in Fig. 3 is prepared. The board is a circuit board made of a laminated board using a bismaleimide triazine resin. Molding temperature 175 ° C, curing time 2
Minutes. The molded product is post-cured at 175 ° C. for 8 hours to obtain a molded product for measuring warpage. 25 ° C, 100 ° C, 175 ° C, 2
After being left in an oven at 00 ° C. and 240 ° C. for 5 minutes, the amount of warpage is measured as shown in FIG. The unit is mm.

<< Examples 2 to 6 >><< Comparative Examples 1 to 5 >> The types and blending amounts of the epoxy resin, the phenol resin curing agent and the spherical silica were determined according to the formulations shown in Tables 1 and 2, and other epoxy silane coupling agents, Carbon black, carnauba wax, brominated phenol novolac type epoxy resin, antimony trioxide and DBU were blended in accordance with the same formulation amount as in Example 1, a molding material was obtained in the same manner as in Example 1, and evaluated in the same manner. The results are shown in Tables 1 and 2. The sample of Comparative Example 5 did not flow and therefore could not be molded and could not be evaluated. The structures of the components used in Examples and Comparative Examples are shown below.

[0019]

[Chemical 5]

[0020]

[Chemical 6]

Table 1 Example 1 2 3 4 5 6 formulation (parts by weight) Epoxy resin A 11.1 Epoxy resin B 10.4 10.0 10.0 11.3 3.5 Epoxy resin C 0.4 Phenolic resin curing agent A 5.3 6.0 5.6 6.4 2.2 Phenol resin curing agent B 6.4 Phenol resin curing agent C 0.4 Spherical silica 80.3 80.3 80.3 80.3 79.0 91.0 Characteristics Curing shrinkage (%) 0.05 0.03 0.12 0.03 0.14 0.01 Thermal expansion coefficient at room temperature (× 10 ^-5 / ° C) 1.31 1.33 1.32 1.38 1.29 0.82 Tg (° C) 182 199 183 185 190 192 Warpage amount: 25 ℃ 0.33 0.32 0.51 0.36 0.72 -0.19 100 ℃ 0.33 0.31 0.49 0.34 0.67 0 175 ℃ 0.32 0.29 0.44 0.28 0.56 0.11 200 ℃ 0.12 0.23 0.56 0.22 0.19 0.24 240 ℃ -0.26 -0.05 0.16 -0.31 -0.25- 0.09

Table 2 Comparative Example 1 2 3 4 5 Compounding (parts by weight) Epoxy resin A 10.8 13.4 1.6 Epoxy resin C 10.8 2.5 Phenolic resin curing agent A 5.6 6.3 1.1 Phenol resin curing agent C 5.6 3.2 Spherical silica 80.3 80.3 91.0 77.0 94.0 Characteristics Curing shrinkage (%) 0.24 0.26 0.29 0.17 ∧ Normal temperature coefficient of thermal expansion (× 10 ^-5 / ℃) 1.29 1.26 0.76 1.54 Evaluation Tg (℃) 175 178 145 193 Valence amount: 25 ℃ 1.35 1.42 -0.03 0.98 Not 100 ℃ 1.33 1.33 0.28 0.88 Yes 175 ℃ 1.25 1.20 0.61 0.59 ∨ 200 ℃ 0.46 0.31 0.44 0.11 240 ℃ -0.01 0.02 0.06 0.03

[0023]

According to the present invention, it is possible to obtain a BGA package having a small amount of warp at -65 ° C to 240 ° C.
It is possible to obtain a good BGA package which has few defects due to the temperature cycle test, has high reliability, and has less troubles during mounting.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between total shrinkage and warpage.

FIG. 2 is a schematic diagram of shrinkage when molded at 175 ° C. and returned to room temperature.

FIG. 3 shows a warped evaluation molded product and an evaluation method.

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Claims (2)

(57) [Claims] 1. An epoxy resin, a phenol resin curing agent,
A resin composition containing 78 to 93% by weight of an inorganic filler and 100% by weight of the total composition as an essential component, wherein an epoxy resin is represented by the following formula 1 and a phenol resin hardener.
The agent is represented by the following formula 2, and the cured product of the resin composition has a cure shrinkage of 0.15% or less and a thermal expansion coefficient of 0.8 × 10 ^{−5 to} 1.5 × 10 ^{−5 at} room temperature. A resin composition for a ball grid array, which has a characteristic of / ° C. [Chemical 1] [Chemical 2] 2. The resin composition for a ball grid array according to claim 1, which has a glass transition temperature of 180 ° C. or higher in addition to the above characteristics.