JPH11288979A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To resin-encapsulate the gap parts between a wiring circuit board and a semiconductor element without both the generation of voids or the like and breakages in solder balls, efficiently in a short time and moreover, simply. SOLUTION: A semiconductor device is characterized by that the device is manufactured by such a method that electrode parts 5 under a semiconductor element 4 area made to contact with wiring electrodes 2 on a wiring circuit board 1 via solders 3, the solders 3 are molten by heating to bond the element 4 to the board 1, then the board 1 mounted with the element 4 is set in a cavity part of a metal mold, an encapsulating resin composition is introduced from the gate part of the metal mold into the cavity part in a state such that the composition is molten under a pressure to pressure- send the composition in gap parts 6 between the above board 1 and the element 4, the gap parts 6 are filled with the composition and the composition is cured to resin- encapsulate the gap parts 6 between the above board 1 and the element 4, and the sealing resin composition contains (a) an epoxy resin, (b) a curing agent and (c) an inorganic filler of the largest particle diameter of 24 μm or smaller as its essential components, (d) the content of the components of the composition is 50 to 85 wt.% of the whole composition as a whole and the molten viscosity of the composition at a molding temperature is 200 poises or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device by a flip-chip method.

[0002]

2. Description of the Related Art In recent semiconductor devices, the number of I / O pins has increased with the improvement in performance, and with the miniaturization of the package size, semiconductor devices using conventional gold wires have been used. The method of connecting the element to the lead frame has not been adopted. In such a situation, recently, a method called a flip chip method for mounting a semiconductor element on a substrate via solder has come to be used in large numbers. In this type of connection method, in order to improve the reliability of the device, a liquid epoxy resin is injected into a gap between the semiconductor device and the substrate and cured to improve the reliability. However, since the resin is filled by utilizing the capillary phenomenon in the gap between the semiconductor element and the substrate, it takes a very long time to fill, and if the viscosity of the resin composition is reduced to shorten the filling time, In addition, there is a problem that the inorganic filler in the encapsulating resin composition is settled at the time of heat curing and the expansion coefficient differs between the upper and lower portions of the cured resin, thereby lowering the reliability of the semiconductor device.

The present invention has solved the above-mentioned problems, and it is possible to reliably fill a gap between a substrate and a semiconductor element with a sealing resin without generating voids and the like, and it is also possible to damage a solder ball. It is an object of the present invention to provide a method of manufacturing a semiconductor device by a flip-chip method, which can perform a resin encapsulation in a short time without any problem, and can obtain a highly reliable semiconductor device having excellent moisture resistance.

[0004]

Means for Solving the Problems and Embodiments of the Invention The present inventors have conducted intensive studies to achieve the above object, and as a result, melted a specific sealing resin composition described later from a mold gate portion. In this state, the gap between the substrate and the semiconductor element is pressure-transferred, filled with the sealing resin composition, and cured by heating (so-called transfer molding) to seal the gap between the substrate and the semiconductor element with the resin. The present inventors have found that it is possible to manufacture a highly reliable semiconductor device that can perform sealing in a very short cycle and that does not cause sedimentation of a filler, and have accomplished the present invention.

That is, according to the present invention, an electrode portion of a semiconductor element is brought into contact with a wiring electrode of a printed circuit board via solder, the solder is heated and melted to join the semiconductor element to the substrate, and then the semiconductor element is mounted. The substrate was set in the cavity of the mold, and the sealing resin composition was introduced into the cavity from the gate of the mold in a molten state under pressure and fed to the gap between the substrate and the semiconductor element, A method of manufacturing a semiconductor device, comprising filling and curing a sealing resin composition to seal a gap between the substrate and the semiconductor element with a resin, wherein the sealing resin composition is (a) ) Epoxy resin, (b) curing agent,
(C) An inorganic filler having a maximum particle size of 24 μm or less is an essential component, and the content of the component (c) is 50 to 85 of the entire composition.
The present invention provides a method for manufacturing a semiconductor device, characterized in that the melt viscosity at a molding temperature is 200 poise or less.

Hereinafter, the present invention will be described in more detail.
In the method for manufacturing a semiconductor device according to the present invention, for example, as shown in FIG. 1, first, an electrode portion 5 of a semiconductor element 4 is applied to a wiring electrode 2 on a substrate 1 on which a wiring circuit is formed on one side via a solder 3. Contact Next, by heating and melting the solder 3,
The semiconductor element 4 is joined to the substrate 1. In this case, the distance between the semiconductor element and the substrate is about 10 to 150 μm, preferably 20 to 100 μm. When the number of electrodes increases, the size of the solder ball decreases, so that the distance is inevitably shortened. In the case of using the manufacturing method of the present invention, it is desirable that the distance is 30 μm or more. FIG. 2 shows an example of solder arrangement.

According to the present invention, the substrate on which the semiconductor element is mounted is set in the mold cavity, and the sealing resin composition is pressed from the mold gate to the cavity in a molten state. Into the gap between the substrate and the semiconductor element under pressure, filling the gap, curing the sealing resin composition (so-called transfer molding), and sealing the gap between the substrate and the semiconductor element with the resin. .

For example, a substrate on which the above-described semiconductor element is mounted is placed in a cavity 13 of a lower mold 12 of a mold 10 having an upper mold 11 and a lower mold 12 as shown in FIG. After setting, the upper mold 11 is closed to keep the temperature. At that time, the temperature of the mold is preferably set to 130 to 200 ° C. When the mold temperature is lower than 130 ° C., the melt viscosity of the encapsulating resin composition becomes high, so that the solder may be washed away during molding or voids may be generated inside. Also, 20
If the temperature is higher than 0 ° C., the reaction may be too fast to completely fill. After that, the sealing resin composition is charged into the plunger pot portion, and pressurized by the plunger 14. The sealing resin composition may be formed into a cylindrical preform before being charged into the pot, or may remain as granular particles. It is desirable to heat the sealing resin composition to 50 to 100 ° C. in advance with a high-frequency preheating device before putting the plunger pot in order to obtain good moldability. The molding pressure is preferably 10 to 100 kgf / cm ² , more preferably 30 to 50 kgf / cm ² .
If the pressure is less than 10 kgf / cm ² , the pressure may be too low to obtain a sufficient filling property.
If it exceeds / cm ² , the solder may be washed away. If the pressure does not cause any trouble, it is desirable to set the pressure as high as possible from the viewpoint of reliability.

[0009] Such a molten sealing resin composition 16
Is introduced from the gate portion 15 of the mold 10 into the cavity portion 13 under the above pressure, and the molten sealing resin composition is pressed into the gap portion 6 between the substrate 1 and the semiconductor element 4 and cured. Then, as shown in FIG. 4, a semiconductor device 18 in which the gap 6 is sealed with a resin 17 is obtained. The curing time is 60 to 240 seconds, preferably 60 to 120 seconds.
As a method of transfer molding, a 3P system (Pre-Pac
Using a molding apparatus using a film known as “kaged-process” can prevent the problem that the resin leaks from the joint between the upper and lower molds. Further, according to this method, since the resin does not come into direct contact with the mold, even if a sealing resin composition containing no release agent is used, no release trouble is caused. Further, there is an advantage that a liquid sealing resin composition can be used.

In this case, the encapsulating resin composition used in the present invention is a so-called curable epoxy resin composition comprising (a) an epoxy resin, (b) a curing agent, and (c) an inorganic filler as essential components. However, typically, it is necessary to seal an element having a gap of 10 to 150 μm and a size of 5 to 20 mm × 5 to 20 mm square and a thickness of 0.1 to 0.6 mm. It is required to have different properties in terms of flow characteristics and curing characteristics from the conventional resin compositions for encapsulating semiconductor devices. In particular, the viscosity during molding is important, and the melt viscosity at the molding temperature needs to be 200 poise or less. For example, when molding at 130 to 200 ° C., preferably 150 to 185 ° C., and more preferably 175 ° C. Has a melt viscosity measured at a molding temperature of 200 poise or less, preferably 5 to 10
0 poise or less, more preferably 10 to 50 poise or less. Further, since it is necessary to inject the resin in about 3 to 30 seconds, the gelling time of the resin is 2 at the molding temperature.
0 seconds or more, preferably 30 seconds or more, more preferably 35
It is better to be more than seconds. The spiral flow as a measure of fluidity is 100 to 250 cm, more preferably 150 when measured at 175 ° C. and a pressure of 70 kgf / cm ^2.
It is preferable that the flow is about 250 cm.

Further, the sealing resin composition will be described in detail. The epoxy resin as the component (a) can be any known epoxy resin having at least two epoxy groups per molecule. Although it can be used, in particular, bisphenol A type epoxy resin, bisphenol type epoxy resin such as bisphenol F type epoxy resin, phenol novolak type epoxy resin, novolak type epoxy resin such as cresol novolak type epoxy resin, cyclopentadiene type epoxy resin, Triphenol alkane type epoxy resin such as triphenol methane type epoxy resin, triphenol propane type epoxy resin, biphenyl type epoxy resin, naphthalene ring-containing epoxy resin,
Examples thereof include a phenol aralkyl type epoxy resin and a biphenyl aralkyl type epoxy resin. Further, an epoxy resin represented by the following structural formula can also be used.

[0012]

Embedded image (G = glycidyl group, Me = methyl group, n is 0 to 10,
(Preferably an integer of 0 to 3)

The total chlorine content in these epoxy resins is 1
It is at most 500 ppm, preferably at most 1,000 ppm. Further, it is preferable that the extraction water chlorine in 20 hours at 120 ° C. and 50% epoxy resin concentration is 5 ppm or less. When the total chlorine content exceeds 1500 ppm and the chlorine content in the extracted water exceeds 5 ppm, the moisture resistance reliability of the semiconductor may be reduced.

As the curing agent (b) of the present invention, any one which can cure a conventionally known epoxy resin such as an acid anhydride, an amine compound, or a phenol resin can be used. Phenolic resin is desirable in terms of reliability. Any phenolic resin can be used as long as it has two or more phenolic hydroxyl groups in one molecule. In particular, bisphenol type resins such as bisphenol A type resin and bisphenol F type resin, phenol novolak resin, cresol novolak Novolak resin such as resin, phenol aralkyl resin, naphthalene ring-containing phenol resin, cyclopentadiene type phenol resin, triphenol methane type resin, triphenol alkane type resin such as triphenol propane type resin, biphenyl type resin, biphenyl aralkyl type resin Those containing a phenolic hydroxyl group having the following structure are exemplified.

[0015]

Embedded image (N is an integer of 0 to 10, preferably 0 to 3)

The phenolic resin, like the epoxy resin, has
Chlorine ions and sodium ions extracted at a temperature of 0 ° C. are all preferably 10 ppm or less, more preferably 5 ppm or less.

The mixing ratio of the epoxy resin to the phenolic resin is such that the phenolic hydroxyl group in the phenolic resin is 0.5 to 1.6 mol, preferably 0.6 to 1.4 mol per 1 mol of the epoxy group in the epoxy resin. It may be molar.
If the amount is less than 0.5 mol, the hydroxyl group becomes insufficient, the homopolymerization ratio of the epoxy group increases, and the glass transition temperature may decrease. On the other hand, if it exceeds 1.6 mol, the ratio of the phenolic hydroxyl group becomes high, and the reactivity is lowered, and the crosslink density is too low to obtain sufficient strength in some cases.

In the sealing resin composition used in the present invention, phosphorus-based, imidazole derivatives, cycloamidine-based derivatives and the like can be used as a curing accelerator. The curing accelerator is used in an amount of 0 to 10 parts by weight, especially 0.1 to 100 parts by weight of the total amount of the epoxy resin and the phenol resin.
It is preferably from 0.01 to 10 parts by weight.

The inorganic filler as the component (c) has a maximum particle size of 24 μm or less, and is produced by, for example, fused silica pulverized by a ball mill or the like, spherical silica obtained by flame melting, a sol-gel method, or the like. Spherical silica,
Crystalline silica, alumina, boron nitride, aluminum nitride, silicon nitride, magnesia, magnesium silicate and the like are used. When the semiconductor element generates a large amount of heat, it is desirable to use alumina, boron nitride, aluminum nitride, silicon nitride, or the like having a large thermal conductivity and a small expansion coefficient as a filler.
Further, it may be used by blending with fused silica or the like.
Above all, it is preferable to use a spherical inorganic filler, usually fused silica, and when thermal conductivity is required, alumina or aluminum nitride.

Taking fused silica or alumina as an example of the inorganic filler, the amount of fused silica or alumina used is 100 parts by weight per 100 parts by weight of the total amount of epoxy resin and curing agent.
It is preferably from 550 to 550 parts by weight, particularly preferably from 200 to 450 parts by weight. If the amount is less than 100 parts by weight, the expansion coefficient cannot be sufficiently reduced. On the other hand, if the amount is more than 550 parts by weight, the viscosity becomes too high and molding may not be performed.

The particle size distribution of the inorganic filler such as silica, alumina and the like used herein has an average particle diameter of 1-1.
5 μm, more preferably 2 to 10 μm, 2 μm in the filler
0 to 60% by weight of a filler such as fused silica or alumina having a fine particle diameter of 5 μm or less, and a maximum particle diameter of 24 μm
Or less, preferably 20 μm or less, more preferably 10 μm
m and a specific surface area by BET adsorption method of 3.5 to 6.0 m ² / g, preferably 4.0 to 5.0.
Those having m ² / g are desirable. If the filler having a particle size of 5 μm or less is less than 20% by weight, the filling property of the gap between the semiconductor element and the substrate is poor, and there is a possibility that a problem such as a void or breakage of a solder bump may be caused. On the other hand, if it is more than 60% by weight, the amount of fine powder becomes too large and the surface of the resin and the filler are not sufficiently wetted. Conversely, the viscosity of the composition becomes high, and it is necessary to increase the pressure at the time of molding. The solder bump may be damaged. Desirably 30 ~
It is preferable that a filler having a particle size of 5 μm or less is contained in the range of 50% by weight. In general, if the maximum particle size of the filler is set to 1/5 or less, preferably 1/10 or less of the distance between the substrate and the semiconductor element, no problem occurs in the filling property. The average particle diameter can be determined as a weight average value (or median diameter) using a particle size distribution measuring device such as a laser light diffraction method.

In the present invention, the particle size is reduced from 3 μm to ultrafine silica (0.00 μm) to reduce the viscosity of the composition and to control the fluidity of the resin composition by the close-packing of the filler and the addition of thixotropy.
A silica filler having a particle size of 5 μm or less, usually 0.001 to 0.05 μm) may be appropriately mixed and blended. For example, the specific surface area represented by Aerosil is 50 to 300 m ² / g.
(Or a finely divided silica filler having a particle size of 0.001 to 0.05 μm), a finely divided silica filler having a particle size of 0.05 to 0.5 μm, and a silica filler having a particle size of 0.5 to 3 μm are appropriately mixed. It is better to use it. With respect to the mixing amount of these finely divided silicas, ultrafine silica is 0 to 5% by weight, silica having a particle size of 0.05 to 0.5 μm is 1 to 15% by weight, and particle size is 0.5 to 0.5% by weight based on the whole inorganic filler. 5 to 20% by weight of silica of ~ 3 µm
The silica mixture may be prepared and blended such that the average particle size of the silica mixture is 1 μm or less.

In this case, in the present invention, the inorganic filler accounts for 50 to 85% by weight, especially 70 to 82% by weight of the whole composition.
It contains. If the amount is less than 50% by weight, the viscosity of the composition becomes low, but the expansion coefficient becomes large, and there is a problem that the sealant peels off on the surface of the semiconductor chip in a temperature cycle test or the like. The viscosity of the product becomes too high, the filling property is deteriorated, and poor filling occurs.

The composition of the present invention contains powders of conventionally known silicone rubber and silicone gel, silicone-modified epoxy resins and silicone-modified phenol resins,
A derivative such as a thermoplastic resin composed of methyl methacrylate-butadiene-styrene and a hydrogenated product thereof may be added as a stress reducing agent.

For the purpose of lowering the viscosity, conventionally known n-butyl glycidyl ether, phenyl glycidyl ether, styrene oxide, t-butyl phenyl glycidyl ether, dicyclopentadiene diepoxide, phenol, cresol, t-butyl phenol A diluent such as can be added.

Further, a flame retardant aid such as brominated epoxy resin or antimony trioxide, a coupling agent such as a silane coupling agent, a titanium-based coupling agent, an aluminum-based coupling agent, or carbon black for flame retardation. In some cases, a coloring agent such as a nonionic surfactant, a fluorinated surfactant, a wetting enhancer such as silicone oil, an antifoaming agent, and the like can be added.

As a production method, the above-mentioned raw materials are uniformly mixed using a high-speed mixer or the like, and then sufficiently kneaded with a hot double roll or a continuous kneader.

[0028]

According to the present invention, the gap between the substrate and the semiconductor element can be reliably filled with the sealing resin composition, and no voids or the like are generated, and the solder balls are not damaged. It is possible to efficiently and easily perform resin sealing in a short time and obtain a highly reliable semiconductor device having excellent moisture resistance.

[0029]

EXAMPLES The present invention will be described below in detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

Examples 1 to 3 and Comparative Examples 1 and 2 The components shown in Table 1 were mixed at the ratios shown in the table. This was mixed with a high-speed mixer for 10 minutes, and then kneaded at 50 to 100 ° C. using a continuous kneader to form a sheet.
After cooling, the mixture was pulverized, tableted into a cylindrical shape, and pelletized to obtain a resin composition (Examples 1 to 3, Comparative Examples 1 and 2). Its characteristics are as shown in Table 2.

[0031]

[Table 1]

[0032]

Embedded image Curing agent (1): Novolak type phenol resin, hydroxyl equivalent: 110 Curing agent (2): Phenol aralkyl resin (MEH7800, manufactured by Meiwa Kasei Co., Ltd.), hydroxyl equivalent: 175 Brominated novolak type epoxy resin: BREN-S (Nippon Kayaku) Epoxy equivalent: 280 Inorganic filler: Average particle size (μm) Maximum particle size (μm) Spherical silica (1) 3 10 Spherical silica (2) 520 Spherical silica (3) 548 Spherical alumina 315 Catalyst (1): triphenylphosphine Catalyst (2): TPP-K (tetraphenylphosphonium tetraphenylborate) Coupling agent: γ-glycidoxypropyltrimethoxysilane Average particle size and maximum particle size of the above-mentioned inorganic filler Is Shirasu (CILASCALTEL (France))
Laser Diffraction Particle Size Distribution Analyzer: Granur
It was measured using an Omter 920.

[0033]

[Table 2]

[0034] Spiral flow molding temperature 175 ° C., it was measured spiral flow by transfer molding at a molding pressure of 70 kgf / cm ^2. Gel time The time until the epoxy resin composition became a gel on a hot plate at 175 ° C. and 160 ° C. was measured. The viscosity at a temperature of 175 ° C. was measured using a nozzle having a diameter of 1 mm under a pressure of 10 kg using a melt viscosity increasing type flow tester. A test piece of 4 × 4 × 15 mm was molded under the conditions of a glass transition temperature, a coefficient of linear expansion of 175 ° C., 70 kgf / cm ² and a molding time of 2 minutes, and was subjected to post-curing at 180 ° C. for 4 hours. It was measured by raising the temperature at 5 ° C / min.

Next, a BT substrate having a thickness of 0.28 mm and 10
A semiconductor device in which a semiconductor element having a size of 10 mm and a thickness of 0.25 mm was joined with 450 solder balls having a diameter of 75 μm was set in a mold heated to 160 ° C. as shown in FIG. Next, each of the resin compositions formed into a cylindrical shape was heated to 65 ° C. by a high-frequency preheater, and then charged into a plunger pot, and then heated at a molding pressure of 40 kgf / cm ² .
Injected over seconds. The injection was cured for 60 seconds, the mold was opened, and the semiconductor device was taken out. The semiconductor device obtained by molding was checked using an ultrasonic flaw detector to determine whether the voids were completely filled with the resin composition or whether there were no voids. Table 3 shows the results.

[0036]

[Table 3]

Further, for comparison of moisture resistance, the semiconductor device used in the examples was encapsulated by using a conventionally used underfill material (epoxy resin composition) for an acid anhydride-curable flip chip. (Comparative Example 3). The following composition was used as an acid anhydride-curable underfill material for flip chips. Bisphenol A type epoxy resin 50 parts by weight 4-methylhexahydrophthalic anhydride 30 parts by weight Spherical silica having an average particle size of 5 μm and a maximum particle size of 15 μm 100 parts by weight 2-phenylimidazole 0.2 parts by weight Evaluation of moisture resistance Example 1 Each of the semiconductor device sealed in Example 1 and the semiconductor device sealed in Comparative Example 3 was placed in a pressure cooker container at 121 ° C. and 2.1 atm, taken out at predetermined time intervals, and sealed with the element surface using an ultrasonic flaw detector. The state of peeling between the resin was observed. Table 4 shows the results.

[0038]

[Table 4]

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a state in which a semiconductor element and a substrate are joined.

FIG. 2 is a plan view showing an example of solder arrangement.

FIG. 3 is a schematic diagram illustrating a state in which a substrate on which a semiconductor element is mounted is sealed with a resin.

FIG. 4 is a schematic sectional view showing an example of a semiconductor device obtained by the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Wiring electrode 3 Solder 4 Semiconductor element 5 Electrode part 6 Void part 10 Die 11 Upper die 12 Lower die 13 Gavity part 14 Plunger 15 Gate part 16 Sealing resin composition 17 Sealing resin 18 Semiconductor apparatus

Claims (1)

[Claims] An electrode portion of a semiconductor element is brought into contact with a wiring electrode of a printed circuit board via solder, the solder is heated and melted to join the semiconductor element to the substrate, and then the substrate on which the semiconductor element is mounted is formed of gold. It is set in the mold cavity, the sealing resin composition is introduced in a molten state from the mold gate to the cavity under pressure, and is pressure-fed into the gap between the substrate and the semiconductor element, filled, and sealed. A method of manufacturing a semiconductor device in which a sealing resin composition is cured to seal the gap between the substrate and the semiconductor element with a resin, wherein the sealing resin composition comprises: (a) an epoxy resin; (B) a curing agent, (c) an inorganic filler having a maximum particle size of 24 μm or less as an essential component, a content of the component (c) is 50 to 85% by weight of the whole composition, and a melt viscosity at a molding temperature. Semiconductor device characterized by having a value of 200 poise or less. Manufacturing method.