JPH11166105A - Resin composition for semiconductor encapsulation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin composition for semiconductor encapsulation of an excellent moldability which prevents, on molding, a gold wire deformation, a lead pin deformation and die pad shift as well as molding flash in spite of large amount of a filler used in a manufacture of a thin semiconductor package. SOLUTION: A resin composition for semiconductor encapsulation comprises a thermosetting resin and an inorganic filler. The inorganic filler mainly consists of a silica powder (A) comprising (a1) a super fine silica powder having an average particle size of 0.01-0.5 μm and (a2) a silica powder having a circularity of 0.8 or more and an accumulated particle size distribution which satisfies the conditions described below (the total of (1) to (3 is 100 wt.%). 1) Particles of a particle size of 5.0 μm or less constitute 5-30 wt.%. (2) Particles of a particle size of 48 μm or less constitute 50 wt.% or more. (3) Particles of a particle size of 100 μm or more constitute 5 wt.% or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor which is free from problems such as gold wire flow, lead pin deformation and die pad shift given to a package at the time of molding, and which has excellent moldability with an excellent effect of suppressing molding burrs. The present invention relates to a sealing resin composition.

[0002]

2. Description of the Related Art Semiconductor devices such as transistors, ICs, and LSIs are encapsulated in plastic packages or the like to form semiconductor devices from the viewpoint of protection from external environments and easy handling of the semiconductor devices. A typical example of this type of plastic package is a dual in-line package (DIP). Recently, in order to improve the portability of electronic devices, thinner packages,
Package thickness of 1.0, such as Think Quad Flat Package (TQFP) and Thin Small Outline Package (TSOP), with advanced miniaturization of lead pins
Thin packages of about 1.4 mm are becoming mainstream.

[0003]

However, such a thin package as described above has a problem that defects at the time of molding, that is, gold wire flow, deformation of lead pins, die pad shift, and the like are easily generated. The cause of this occurrence is
This is because these thin packages are sealed with a resin composition containing a large amount of an inorganic filler in order to prevent solder resistance in the surface mounting process.
In other words, this is because a resin composition filled with a large amount of filler to near the limit is used for the purpose of suppressing moisture absorption of the package and improving the resin strength. When such a resin composition is used, the fluidity is remarkably reduced, which causes various problems in molding as described above.

In order to solve such a problem, it has been studied to improve the fluidity of the resin by making the shape of the filler a shape close to a true sphere or by mainly using a filler having a large particle diameter. I have. Further, in order to enable high-density packing, a grain size design applying a Hudson model is used.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and in the molding of a thin semiconductor package, despite the use of highly filled fillers, the flow of gold wires during molding, deformation of lead pins, and die pad shift. It is an object of the present invention to provide a resin composition for semiconductor encapsulation having excellent moldability, in which generation of molding is suppressed and generation of molding burrs is suppressed.

[0006]

Means for Solving the Problems In order to solve the above-mentioned object, a resin composition for semiconductor encapsulation of the present invention is a resin composition for semiconductor encapsulation containing a thermosetting resin and an inorganic filler. In addition, the inorganic filler has a configuration in which the following silica powder (A) is a main component. (A) A silica powder comprising the following (a1) and (a2), and a mixing ratio of both ((a1) / (a2))
Is (a1) / (a2) = 0.1 / 99.9-
Silica powder set in the range of 1.0 / 99.0. (A1) Ultrafine silica powder having an average particle size of 0.01 to 0.05 μm. (A2) Silica powder having a roundness of 0.8 or more and a particle size distribution set to the following cumulative particle size distribution (provided that the total cumulative particle size distribution is 100% by weight). 5 to 30% by weight having a particle size of 5.0 μm or less. Those with a particle size of 48 μm or less are 50% by weight or more. 5% by weight or less of particles having a particle size of 100 μm or more.

In order to achieve the above object, the present inventors have conducted a series of studies focusing on the composition of a thermosetting resin composition used for encapsulating a semiconductor device. As a result, as the silica powder used as the inorganic filler, an ultrafine silica powder [(a1)] having a very small average particle diameter of 0.01 to 0.05 μm and a roundness of 0.8 were used. Above and high,
When the silica powder mixed with the silica powder [(a2)] having a small unevenness whose cumulative particle size distribution is set in the above specific range so as to have the above specific mixing ratio (weight ratio), the unevenness of the above unevenness is obtained. The ultrafine silica powder [(a1)] having the above-mentioned fine particle diameter enters between the small silica powder [(a2)] and is in a state of high density packing. The present inventors have found that the flow of gold wires, deformation of lead pins, die pad shift, and the like in the package during molding are suppressed, and that the occurrence of molding burrs is effectively suppressed.

In the present invention, it is preferable to use a fused silica powder as the silica powder (a2).

[0009]

Next, the present invention will be described in detail.

The resin composition for encapsulating a semiconductor of the present invention can be obtained by using an inorganic filler mainly composed of a specific silica powder together with a thermosetting resin.
It is in the form of a powder or a tablet obtained by compressing it. In the present invention, the term “inorganic filler containing a specific silica powder as a main component” is intended to include the case where the inorganic filler is composed of only a specific silica powder.

The thermosetting resin is not particularly limited, and various conventionally known thermosetting resins can be used. Among them, an epoxy resin is preferably used.

The epoxy resin preferably has two or more epoxy groups in one molecule. For example, cresol novolak epoxy resin, phenol novolak epoxy resin, bisphenol A epoxy resin, biphenyl epoxy resin Resins. These may be used alone or in combination of two or more.
Among them, those having an epoxy equivalent of 100 to 300 and a softening point of 50 to 130 ° C. are particularly preferably used.
Further, as the epoxy resin used in the present invention, in addition to the above-mentioned conditions, from the viewpoint of moisture resistance reliability, those having lower contents of ionic impurities and hydrolyzable ions are particularly preferably used. Specifically, the free sodium ion concentration and the chloride ion concentration are each 5 ppm
Or less and a hydrolyzable chloride ion concentration of 600
ppm or less of epoxy resin.

When an epoxy resin is used as the thermosetting resin, a phenol resin is usually used together with the epoxy resin. The phenol resin acts as a curing agent for the epoxy resin, and is not particularly limited, and various phenol resins are used. For example,
Phenol novolak resins, among which, as the phenol novolak resin, a hydroxyl equivalent of 70 to
It is preferable to use those having a softening point of 150 to 150 ° C.

The mixing ratio of the epoxy resin and the phenol resin is preferably set such that the hydroxyl group in the phenol resin is 0.5 to 2.0 equivalent per 1 equivalent of the epoxy group in the epoxy resin. More preferably,
It is in the range of 0.8 to 1.2 equivalents.

[0015] In the inorganic filler mainly composed of a specific silica powder used together with the thermosetting resin, the specific silica powder (A) has the following (a)
It is a silica powder consisting of 1) and (a2).

(A1) The average particle size is 0.01 to 0.05 μm
Ultrafine silica powder set to m. (A2) Silica powder having a roundness of 0.8 or more and a particle size distribution set to the following cumulative particle size distribution (provided that the total cumulative particle size distribution is 100% by weight). 5 to 30% by weight having a particle size of 5.0 μm or less. Those with a particle size of 48 μm or less are 50% by weight or more. 5% by weight or less of particles having a particle size of 100 μm or more.

In the above silica powder (a2), a roundness of 0.8 or more is defined as a roundness of 0.8 or more, which is closer to a perfect circle, in the definition of the roundness described below. That is to be done. The roundness is calculated as follows. That is, in a projected image 1 (see FIG. 1 (a)) of an object whose roundness is to be measured, the actual area is α and the length of the periphery of the projected image 1 is PM. Assume a projected image 2 (see FIG. 1 (b)) of a perfect circle having the same PM as the circumference of 1. Then, the area α ′ of the projection image 2 is calculated. Next, the ratio (α / α ′) between the real area α of the projection image 1 and the area α ′ of the projection image 2 indicates roundness, and this value (α / α ′) is calculated by the following equation (1).
Is calculated by Therefore, the roundness of 1.0 is
As is clear from this definition, it can be said that it is a perfect circle.
Then, the more irregularities around the object, the smaller the roundness becomes sequentially smaller than 1.0.

[0018]

(Equation 1)

In the cumulative particle size distribution of the silica powder (a2), the particle size is preferably 5.0 μm or less, and the range of the particle size is preferably 0.2 μm or more and 5.0 μm or less. The particle size of the particles having a particle size of 48 μm or less is 50% by weight or more.
Those having a size of less than μm are in the range of 50 to 75% by weight. Those having a particle size of 100 μm or more are 5% by weight or less, and those having a particle size of 100 μm or more are more preferably 3% by weight or less. In the cumulative particle size distribution described above, for example, 50% by weight or more of those having a particle size of 48 μm or less means that the cumulative weight% includes those having a particle size of 5.0 μm or less.

As described above, the ultrafine silica powder [(a1)] having a small average particle diameter of 0.01 to 0.05 μm as the silica powder and the high fineness having a roundness of 0.8 or more are used. The use of silica powder [(a2)] having a roundness and a specific cumulative particle size distribution and using a silica powder (A) in which the mixing ratio of both is set in a specific range allows the high roundness described above. Silica powder with small irregularities [(a
2)] In the meantime, the ultrafine silica powder having a small particle size described above [(a
1)] enters and is in a state of high-density filling, and the fluidity is good in spite of high filling. As a result, gold wire flow in the package at the time of molding, deformation of lead pins, die pad shift and the like occur. It is suppressed, and the generation of molding burrs is effectively suppressed.

The average particle size is 0.01 to 0.0
Mixing ratio of silica powder (a1) having a small particle size of 5 μm and silica powder (a2) having a roundness of 0.8 or more and having a specific cumulative particle size distribution [(a1) / (a
2)] is (a1) / (a2) = 0.1 / 9 in weight ratio.
It must be set in the range of 9.9 to 1.0 / 99.0. That is, when the ultrafine silica powder (a1) is less than 0.1 [the silica powder (a2) exceeds 99.9], a lot of burrs are generated during molding, and conversely, the ultrafine silica powder (a1)
Is more than 1.0 [the silica powder (a2) is less than 99.0], the fluidity of the resin composition is reduced, and the flow of gold wires in the package, deformation of lead pins, die pad shift and the like are likely to occur. It is.

The specific silica powder (A) is, for example,
It can be obtained by mixing silica powders set in the following cumulative particle size distributions (x) to (z). That is, a mixture of the silica powders set in the following cumulative particle size distributions (x) to (z) becomes the specific silica powder (A). (X) the circularity is 0.8 or more, and the average particle size is 25 to 45;
69-95% by weight in the range of μm. (Y) the circularity is 0.8 or more, and the average particle size is 0.2 to 2;
4 to 30% by weight in the range of 0 μm. (Z) 0.1 to 1% by weight having an average particle size in the range of 0.01 to 0.05 μm.

Further, in the present invention, the inorganic filler component may be constituted only by the specific silica powder (A), or may be used in combination with an inorganic filler other than the specific silica powder (A). Good. As the inorganic filler other than the specific silica powder (A), alumina, aluminum nitride,
Talc, calcium carbonate and the like. in this way,
When the inorganic filler other than the above specific silica powder (A) is used in combination, the ratio of the other inorganic filler is preferably set to be 10% by weight or less of the entire inorganic filler component.

The content of the inorganic filler containing the specific silica powder (A) as a main component is preferably set in the range of 70 to 95% by weight, particularly preferably 80 to 95% by weight, based on the whole epoxy resin composition. ~ 92% by weight. That is, if the content of the inorganic filler is too small, the solder resistance of the package tends to decrease. Conversely, if the content is too large, the flowability decreases, and the wire flow in the package, die pad shift, and deformation of the lead pins are reduced. This is because there is a tendency to occur frequently.

In the resin composition for encapsulating a semiconductor of the present invention, in addition to the above-mentioned thermosetting resin and an inorganic filler mainly composed of a specific silica powder (A), a silane coupling agent, if necessary, Various additives such as a curing accelerator, a release agent, a flame retardant, a flame retardant auxiliary, and a coloring agent such as carbon black are appropriately blended.

Examples of the silane coupling agent include γ-glycidoxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane and the like.

Examples of the curing accelerator include imidazoles such as 2-methylimidazole, tertiary amines, and organic phosphorus compounds.

Examples of the release agent include long-chain carboxylic acids such as stearic acid and palmitic acid, metal salts of long-chain carboxylic acids such as zinc stearate and calcium stearate, and waxes such as carnauba wax and montan wax. .

Examples of the flame retardant include a novolak type brominated epoxy resin and a bisphenol A type brominated epoxy resin.

Examples of the flame retardant aid include antimony trioxide and antimony pentoxide.

The resin composition for encapsulating a semiconductor of the present invention further contains, in addition to the above additives, an ion trapping agent such as hydrotalcite for the purpose of improving reliability in a moisture resistance reliability test. You may.

The resin composition for semiconductor encapsulation of the present invention can be produced, for example, as follows. That is, the thermosetting resin, the inorganic filler mainly composed of the specific silica powder (A), and various additives as necessary are blended at appropriate ratios, and kneading with a mixing roll machine or the like. It is kneaded in a heated state by a machine and melt-mixed. Then, after cooling to room temperature, it can be manufactured by a series of steps of pulverizing by a known means and tableting as required.

Of the above specific silica powder (A), the silica powder (a2) is prepared by, for example, appropriately mixing several types of fillers having different particle size distributions and roundnesses into a desired particle size distribution. Can be obtained. Then, by mixing the ultrafine silica powder (a1) and the silica powder (a2) at the above-described specific ratio, it is possible to obtain a specific silica powder (A) which is a characteristic configuration of the present invention. it can.

The method for encapsulating a semiconductor element using the resin composition for encapsulating a semiconductor obtained by the above-mentioned production method is not particularly limited, and may be carried out by a known molding method such as ordinary transfer molding. it can. The semiconductor device thus obtained is sealed with a resin composition having excellent moldability despite high blending, using an inorganic filler containing the specific silica powder (A) as a main component. In addition, a highly reliable semiconductor device in which the flow of gold wires during molding, the deformation of lead pins, and the occurrence of die pad shift are suppressed, and the occurrence of molding burrs is also effectively suppressed can be obtained.

Next, examples will be described together with comparative examples.

First, prior to the preparation of the epoxy resin composition, the following components were prepared.

[Epoxy resin] o-cresol novolak type epoxy resin (epoxy equivalent 195, softening point 70
℃)

[Phenol resin] Phenol novolak resin (hydroxyl equivalent 105, softening point 83 ° C)

[Curing accelerator] 2-methylimidazole

[Inorganic fillers A to E] First, particle size distribution,
Six types of fused silica powders A to F were prepared by mixing fillers having different roundnesses. The results of roundness and particle size distribution of these six types of inorganic fillers (mixed fused silica powder) A to F are shown in Table 1 below.

[0041]

[Table 1]

[Ultra fine silica powder] Average particle size 0.04μ
m silica powder

[Silane coupling agent] γ-glycidoxypropyltrimethoxysilane

[Releasing agent] Carnauba wax

[Flame retardant] Novolak type brominated epoxy resin (epoxy equivalent: 275, softening point: 84 ° C.)

[Flame retardant aid] Antimony trioxide

[0047]

Examples 1 to 6 and Comparative Examples 1 to 6 The raw materials shown in the following Tables 2 and 3 were mixed in the proportions shown in the same table and kneaded at 100 ° C. for 3 minutes using a mixing roll machine to form a sheet composition. I got something. Then, the sheet-like composition was pulverized to obtain a target powdery epoxy resin composition.

[0048]

[Table 2]

[0049]

[Table 3]

Using each of the above epoxy resin compositions, a spiral flow value, a molding burr amount, a die pad shift generation amount, a gold wire flow generation amount, and a pin deformation amount were measured according to the following methods. The results are shown in Tables 4 to 6 below.

[Spiral Flow Value] The spiral flow value was measured under the conditions of 175 ° C. × 70 kg / cm ² using a mold conforming to the EMMI standard.

[Molding burr] 5 μm thick and 50 μm thick
175 using each mold with a respective slit of m
Molding was performed under molding conditions of 70 ° C. × 70 kg / cm ² , and the flow length of the epoxy resin composition was measured.

[Amount of Die Pad Shift] Using each of the above epoxy resin compositions, a 144-pin sink quad flat package (14) having a 10 mm square die pad 10 having a shape shown in FIG.
4p-TQFP: size 20 mm x 20 mm x thickness 1.
4 mm), the package 11 was cut (indicated by a dashed-dotted line indicates the cut surface), the cut surface was observed, and the amount of deformation of the die pad was measured based on the difference from the design value of the die pad. That is, as shown in FIG. 3A, the thickness (thickness a μm) of the resin layer under the four corners of the die pad 10 was measured for the package in which the die pad shift occurred. On the other hand, as shown in FIG. 3B, in a package in a normal state where no die pad shift occurs,
The thickness (thickness bμ) of the resin layer below the four corners of the die pad 10
m) was measured. Such a measurement is performed at all four corners of the die pad 10, and the difference between these measured values and the normal product (a-
b) was obtained as an absolute value, and this was shown as an average value.

[Amount of Gold Wire Flow] As shown in FIG.
14 having the 10 mm square die pad 10 used above
4p-TQFP frame with gold wire (25μm in diameter)
× maximum length 2.5 mm) 14 and resin-sealed with the epoxy resin composition to prepare a package. In FIG. 4, 15 is a semiconductor chip, and 16 is a lead pin. Then, the flow rate of the gold wire of the produced package was measured using an X-ray analyzer. The measurement was performed by selecting 10 gold wires from each package and measuring the flow rate of the gold wire 14 from the front as shown in FIG. Then, the value that is the maximum part of the flow rate of the gold wire 14 is determined as the value of the flow rate of the gold wire of the package (dmm).
And the gold wire flow rate [(d / L) × 100] was calculated.
L indicates the distance (mm) between the gold wires 14.
Five packages were measured for each epoxy resin composition, and the average value was defined as the amount of gold wire flow.

[Pin deformation amount] The above 144p-TQFP
Was cut into the shape shown in FIG. 6, and the cut surface was observed with a microscope to measure the amount of deformation of the lead pin 16. That is, as shown in FIG. 7, the deformation amount of the lead pin 16 in the sealing resin 18 is the difference (x μm) between the position of the lower surface of the lead pin 16 and the position of the tip of the deformed lead pin 16.
Was measured to evaluate how much the lead pin was deformed. This was measured for five packages for each epoxy resin composition, and the average value was defined as the pin deformation.

[0056]

[Table 4]

[0057]

[Table 5]

From the above Tables 4 and 5, it can be seen that the Example product has a spiral flow value substantially equal to or higher than that of the Comparative product and has good fluidity. further,
Since the length of the molding burr is also very small as compared with the comparative example, it is clear that the molding quality of the package is also excellent. Also, with respect to the die pad shift, the shift amount is smaller than that of the comparative example product.
It had good molding quality.

More specifically, Comparative Examples 1 and 2 using inorganic fillers C and D having a distribution deviating from the cumulative particle size distribution, which is a characteristic configuration of the present invention, have a spiral flow which is smaller than that of the product of the Example. Good, but the molding burr did not stop sufficiently, and the comparative example 1 product having a large average particle size of the filler,
A large pin deformation was confirmed. In Comparative Example 3 using an inorganic filler having a small roundness, the spiral flow value was small, indicating that the fluidity was poor, and the die pad shift amount, the gold wire flow, and the pin deformation amount were large. It is clear that the package quality is inferior. Further, in Comparative Example 4 having a large average particle diameter, good results were obtained with respect to fluidity, but the filler having a large particle diameter tended to be clogged in the gap between the lead pins, resulting in pin deformation and die pad shift. Due to this, the package quality was inferior. In Comparative Example 5 using no ultrafine inorganic filler, which is a feature of the present invention, molding burrs did not stop sufficiently, and in Comparative Example 6 using excessive ultrafine particles, fluidity was low. As a result, die pad shift, gold wire flow, and pin deformation occurred.

[0060]

As described above, the resin composition for encapsulating a semiconductor of the present invention contains, in addition to the thermosetting resin, an inorganic filler mainly composed of the specific silica powder (A). For this reason, among the specific silica powders (A), the ultrafine silica powder [(a1)] having a small particle diameter enters between the silica powders [(a2)] having small irregularities, and becomes a state of high density filling. Even if the inorganic filler is highly filled, regardless of the high filling, the fluidity is good, and as a result, the occurrence of gold wire flow, deformation of lead pins, die pad shift, etc. in the package during molding is suppressed, Moreover, the occurrence of molding burrs is effectively suppressed.

Such a resin composition for encapsulating a semiconductor of the present invention is suitably applied to all semiconductor devices.
Among them, for example, it is most suitable as a sealing material for a thin semiconductor device having a thickness of about 1.0 to 2.0 mm.

[Brief description of the drawings]

FIGS. 1A and 1B are explanatory diagrams showing a method for measuring the roundness of silica powder.

[FIG. 2] 144 molded using an epoxy resin composition
It is a front view showing p-TQFP.

3A and 3B are explanatory views showing a method for measuring a die pad shift, wherein FIG. 3A is a cross-sectional view showing a state where a die pad shift has occurred, and FIG. 3B is a cross-sectional view showing a normal state.

FIG. 4: 144p- used to measure the gold wire flow rate
It is a front view which shows TQFP.

FIG. 5 is an explanatory diagram showing a method of measuring a gold wire flow rate.

FIG. 6 is a sectional perspective view showing a 144p-TQFP cut into a predetermined shape used for measuring a pin deformation amount.

FIG. 7 is an explanatory view showing a method of measuring a pin deformation amount.

Claims (4)

[Claims] 1. A resin composition for encapsulating a semiconductor comprising an inorganic filler together with a thermosetting resin, wherein the inorganic filler comprises the following silica powder (A) as a main component. A resin composition for semiconductor encapsulation, comprising: (A) A silica powder comprising the following (a1) and (a2), and a mixing ratio of both ((a1) / (a2))
Is (a1) / (a2) = 0.1 / 99.9-
Silica powder set in the range of 1.0 / 99.0. (A1) Ultrafine silica powder having an average particle size of 0.01 to 0.05 μm. (A2) Silica powder having a roundness of 0.8 or more and a particle size distribution set to the following cumulative particle size distribution (provided that the total cumulative particle size distribution is 100% by weight). 5 to 30% by weight having a particle size of 5.0 μm or less. Those with a particle size of 48 μm or less are 50% by weight or more. 5% by weight or less of particles having a particle size of 100 μm or more. 2. The above-mentioned silica powder (A) comprises the following (x)
The resin composition for semiconductor encapsulation according to claim 1, which is a mixture of silica powders set to the cumulative particle size distribution shown in (z). (X) the circularity is 0.8 or more, and the average particle size is 25 to 45;
69-95% by weight in the range of μm. (Y) the circularity is 0.8 or more, and the average particle size is 0.2 to 2;
4 to 30% by weight in the range of 0 μm. (Z) 0.1 to 1% by weight having an average particle size in the range of 0.01 to 0.05 μm. 3. The resin composition for semiconductor encapsulation according to claim 1, wherein the silica powder (a2) is a fused silica powder. 4. The resin composition for semiconductor encapsulation according to claim 1, wherein the thermosetting resin is an epoxy resin.