JPH0669259A - Resin tablet for sealing semiconductor - Google Patents

Abstract

PURPOSE:To provide a resin tablet for sealing semiconductor which can obtain a semiconductor device having reduced voids in sealing resin and excellent moisture resistant reliability by applying to a runnerless type transfer molding. CONSTITUTION:A resin tablet 7 for sealing semiconductor is melted and press- fitted in a cavity 2 (2a, 2b) through a gate 3 (3a, 3b) by charging in a pot 1 of a runnerless type mold, and comprises composition containing thermosetting resin and inorganic filler in such a manner that a melted viscosity at a mold temperature to be melted and press-fitted is set to a range of 500-1,000 poise and a tableting density is set to 90% or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor encapsulation resin tablet used for resin encapsulation of a semiconductor by a runnerless system (also called a multi-plunger system) which is a type of transfer molding.

[0002]

2. Description of the Related Art In conventional transfer molding for resin-sealing a semiconductor, a pot having a plunger, a large number of runners radially radiating from the pot, and a runner communicating with each runner are provided. Using a molding die having a large number of cavities, place one semiconductor element assembly structure in each cavity of this die, and insert a resin tablet into the above pot and heat it with the die heat. A system is adopted in which the pressure is applied by a plunger while melting and is melt-pressed into each cavity through the runner and the gate.

In this molding method, however, the resin charged into the pot remains in the pot and each gate as well as in the runner having a long and wide cross-sectional area, so that the resin loss after molding becomes very large. There is.

On the other hand, in recent years, a plurality of pots having plungers are provided for runnerless transfer molding, and the sealing resin injected into each pot is directly passed through the runner. Attempts have been made to perform resin sealing of semiconductors by using a molding die of a system in which each cavity is melt-pressed through (see FIG. 1). This molding method has an advantage that the material cost can be significantly reduced because there is no resin loss due to the runner as in the conventional case.

However, in such a runnerless molding method, bubbles (hereinafter referred to as voids) are easily generated inside the encapsulating resin, which leads to a decrease in the moisture resistance reliability of the semiconductor device and mechanical strength. It is a cause of the decrease of the.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems in transfer molding of the runnerless system, which is far more advantageous in terms of material cost as described above, and reduces voids inside the sealing resin. It is intended to obtain a semiconductor device having excellent moisture resistance reliability.

[0007]

As a result of earnest studies for the above object, the present inventors have found that in runnerless transfer molding, the melt viscosity of the resin tablet used for the transfer molding is the bonding wire in the semiconductor element assembly structure. It also has a significant effect on the occurrence of wire breakage and defective products, as well as the generation of voids inside the encapsulating resin.When this melt viscosity is set to a specific range, and when the tableting tableting density is set to a specific range, The present invention has been completed, knowing that a highly reliable semiconductor device in which the number of defects is small and the occurrence of defective products as described above is not obtained is obtained.

That is, the present invention has a pot and a gate directly connected to the pot at one end thereof and at the other end of which a semiconductor element assembly structure is arranged, that is, a gate directly connected thereto, that is, a runnerless molding die. A resin sealing tablet for semiconductor encapsulation, which is charged into the pot and melt-pressed into the cavity through the gate, comprising a composition containing a thermosetting resin and an inorganic filler, and The melt viscosity at the mold temperature for melt injection is 500-
It is in the range of 1,000 poise and has a tableting density of 9
The present invention relates to a semiconductor encapsulating resin tablet characterized by being 0% or more.

In this specification, the melt viscosity of the resin tablet means that the composition 2 g constituting the tablet is molded into a size (tablet) having a cross-sectional diameter of 10 mm and a height of 15 mm, and this molding material is used to make Shimadzu. Company-made high-performance flow
Tester (nozzle diameter 1mm, nozzle length 10mm, load 10
Kg / cm ² ) means a value measured at a predetermined temperature (mold temperature).

Further, the above-mentioned tableting density means a molding density at the time of room temperature compression molding from a composition containing a thermosetting resin and an inorganic filler, and [tablet density (g / cm ³ )
/ Resin cured product density (g / cm ³ )] × 100%. Where the tablet density is
Calculated by weight of tablet (g) / volume of tablet (cm ³ ), and density of the above-mentioned resin cured product, by weight of resin cured product (g) / volume of resin cured product (cm ³ ). To be

[0011]

The composition for forming a resin tablet used in the present invention comprises a thermosetting resin and an inorganic filler as essential components, and usually contains a curing agent suitable for the type of thermosetting resin. A curing accelerator is blended, and if necessary, additives such as a silane coupling agent, a release agent, and a coloring agent are added and mixed with or without heating.

This composition usually has an average particle size of 0.1 to 10.
It is generally suitable for runnerless transfer molding by crushing to a size of about 0.5 mm and cold-pressing according to the usual method, with a cross-sectional diameter of 4.5-25 mm and height of 5-30 mm.
Although a resin tablet having a cylindrical shape of a certain degree is used, the tablet may have another shape such as a prism shape in addition to the cylindrical shape.

In the present invention, the melt viscosity of such a resin tablet is in the range of 500 to 1,000 poise at the molding die temperature (usually 150 to 200 ° C., preferably 160 to 190 ° C.) as described above. The greatest feature point is to set so that In other words, when the viscosity range is set, put it in the pot and
Since the entrainment of air at the time of melt press-fitting into the cavity through the cavity is suppressed, the inside of the sealing resin that is melt-pressed into the cavity and hardened so as to cover the semiconductor element assembly structure arranged here is Almost no generation of voids is observed. In addition, in the above viscosity range, there is no fear that the fluid resistance applied to the semiconductor element assembly structure when melt-pressed into the cavity becomes too large, and there is no particular concern about causing physical damage to the structure.

On the other hand, the conventional resin tablet is
Since the melt viscosity was usually set to a low value of 200 poises or less from the viewpoint of melt press-fitting property, it was unavoidable to prevent the entrainment of air at the time of charging the pot, which caused a lot of voids in the sealing resin. I think that the. As the melt viscosity is increased, the above problems are reduced, but below 500 poise, satisfactory results cannot be obtained. On the other hand, if the melt viscosity is set too high and exceeds 1,000 poise, which is out of the specified range of the present invention, the fluid resistance becomes large, and the wire breakage or bending of the bonding wire in the semiconductor element assembly structure occurs. It is impossible to avoid a fatal defect such as a short circuit failure.

The melt viscosity of the resin tablet of the present invention is
The above-mentioned specific range can be easily set by, for example, appropriately adjusting the melt viscosity of the thermosetting resin used and the amount of the inorganic filler used. The most typical thermosetting resin is epoxy resin,
The melt viscosity of this epoxy resin is 1 considering the mold temperature.
Generally, it is preferably in the range of 15 to 30 poises at a temperature of 50 ° C. Further, the inorganic filler has a higher melt viscosity of the tablet as the amount thereof increases, but it is generally preferable that the amount of the inorganic filler is 72 to 80% by weight in the tablet. The melt viscosity of the epoxy resin means a value measured by an Oswald viscometer.

As such an epoxy resin, a cresol novolak type epoxy resin having an epoxy equivalent of 175 to 300 and a halogenated phenol novolak type epoxy resin can be preferably used. In the case of an epoxy resin, an appropriate curing agent is required, but preferable examples of the curing agent include novolak type phenol resin such as cresol novolak resin and phenol novolak resin. In addition, curing accelerators usually used with these curing agents include 2-methylimidazole, boron trifluoride,
Examples include triphenylphosphine.

As the above-mentioned inorganic filler, quartz glass powder, silicon dioxide powder and the like are preferably used, but other conventionally known calcium silicate, aluminum nitride, zircon oxide, clay, calcium carbonate, antimony oxide are also used. It is also possible to use powders of alumina, alumina, silicon carbide, glass fibers and the like. Generally, the average particle size of the inorganic filler is preferably about 5 to 20 μm.

The resin tablet of the present invention is characterized by having a melt viscosity in a specific range as described above, and the tableting density, that is, the molding density when cold-pressed from the composition powder is 90% or more, It is also characterized by preferably being 93% or more. When the tableting density is lower than 90%, the amount of air contained in the pot is increased, and the effect of reducing voids due to the regulation of melt viscosity is impaired.

Next, a method of resin-sealing a semiconductor by runnerless transfer molding using the resin tablet having the above-described structure of the present invention will be described with reference to FIGS.

FIG. 1 shows a cross-sectional structure of a runnerless transfer molding die including an upper die 10 and a lower die 11. A plurality of pots are arranged continuously at a predetermined interval in the direction perpendicular to the plane of the drawing. 1 and a gate 3 having one end directly connected to each port 1 and the other end directly connected to a cavity 2 (2a, 2b).
Plungers 4 are provided in each of the pots 1 having a configuration (3a, 3b).

The size of each of the above-mentioned constituent elements differs depending on the size of the semiconductor to be resin-sealed. For example, the pot 1 is designed in a shape and size corresponding to the resin tablet 7, and the gate is designed. 3 has a cross-sectional area of usually 0.6-1.
It is designed to have a length of 0 mm ² and generally a length of 5 to 15 mm. In addition, this size is (A), (B) of FIG. 3 described later.
The same applies to the case of using another molding die as shown in FIG.

The above cavity 2 of such a molding die
In a and 2b, a semiconductor element assembly structure including a plurality of semiconductor elements arranged in the lead frames 5a and 5b at a predetermined interval in the direction perpendicular to the plane of the drawing, and an external lead or bonding wire surrounding the semiconductor elements. 6a, 6b (for example, 16 Pin
(DIP, 42 Pin DIP, power transistor, etc.) are arranged, while each pot 1 is charged with the resin tablet 7 of the present invention, and is pressurized by the plunger 4 while being heated at the mold temperature. The mold temperature at this time is usually 150 to 200 ° C., preferably 160 to 190 ° C., as described above. The plungeer pressure is generally 50 to 120 kg / cm ² , preferably 70 to 1
It is set to 00 kg / cm ² .

By the above heating and pressurization, the resin tablet 7 is melted, and the cavity 2 is passed through the gates 3a and 3b.
It is press-fitted into a and 2b, and the semiconductor element assembly structures 6a and 6b arranged therein are cured while being entirely covered. At this time, since the melt viscosity and the tableting density of the resin tablet 7 are within the above-mentioned specific ranges, almost no voids are found in the cured resin, and there is no possibility of causing physical damage to the assembly structures 6a and 6b. Absent.

FIG. 2 shows a state in which the transfer molding has been carried out as described above, and then the mold has been released from the molding die including the upper mold 10 and the lower mold 11. Reference numerals 20a and 20b respectively show reels. It is a cured encapsulating resin that covers the semiconductor element assembly structures 6a and 6b arranged at a predetermined interval on the dframes 5a and 5b. Incidentally, 30a and 30b are resins cured in the respective gates 3a and 3b, and 100 is a resin cured in the respective pots 1. These resin portions 30a, 30b, 100 are molding loss, but since there is no runner, there is no resin loss in this runner portion, and the material cost can be reduced accordingly.

In the molding die shown in FIG. 1, 1
The cavities 2a and 2b are directly connected to the other ends of the gates 3a and 3b, respectively, one end of which is directly connected to the one port 1, but the cavities that are directly connected to the one port 1 through the gate 3 are used. The number of 2 can be freely selected in the range of generally 1 to 6, preferably 2 to 4. For example, FIGS. 3A and 3B show this example.

That is, as shown in FIG. 3A, one pot 1 is directly connected to four cavities 2c, 2d, 2e, 2f via gates 3c, 3d, 3e, 3f. Alternatively, as shown in FIG. 3B, the gates 3g and 3h whose one ends are directly connected to one pot 1 are bifurcated, and two cavities 2g are provided at both ends thereof.
You may take the structure which connects 2g 'and 2h, 2h' directly.

[0027]

As described above, according to the present invention, as the resin tablet for runnerless transfer molding, the melt viscosity and the tableting density thereof are set in a specific range, so that the semiconductor element assembly structure is molded at the time of molding. It is possible to reduce voids inside the encapsulating resin without causing damage, and thus it is possible to obtain a resin-encapsulated semiconductor device having excellent moisture resistance reliability and the like.

[0028]

EXAMPLES Next, examples of the present invention will be described to explain more specifically. In the following, "parts" means "parts by weight".

Example 1 Epoxy equivalent of 19 having a melt viscosity of 25 poises at 150 ° C.
20 parts of cresol novolak type epoxy resin (hereinafter referred to as epoxy resin A) of No. 5, 10 parts of novolak type phenol resin, 96 parts of silicon dioxide powder, 0.5 part of 2-methylimidazole, 0 of carnauba wax 0.5 part, carbon black 0.5 part and silane coupling agent 0.5 part were mixed, and the mixture was heated and kneaded for 5 minutes in a heating roller at 90 ° C., then cooled and ground to an average particle diameter of 0.1. An epoxy resin composition powder of ˜0.5 mm was obtained.

This powder was subjected to room temperature compression molding with a tableting machine,
A cylindrical resin tablet having a cross-sectional diameter of 9.8 mm, a height of 13 mm and a weight of 1.77 g was manufactured. 17 of this tablet
The melt viscosity at 5 ° C. was 800 poise and the tableting density was 95%. This tablet was used as a semiconductor encapsulating resin tablet of the present invention.

Example 2 The epoxy resin composition powder prepared in Example 1 was compression-molded at room temperature with a tableting machine to give a cross-sectional diameter of 9.8 mm and a height of 14.2.
A cylindrical resin tablet having a size of mm and a weight of 1.75 g was manufactured. The melt viscosity of this tablet at 175 ° C. was 805 poise and the tableting density was 90%. This tablet was used as a semiconductor encapsulating resin tablet of the present invention.

Example 3 Instead of the epoxy resin A, the melt viscosity at 150 ° C. was 1
An epoxy resin composition powder was prepared in the same manner as in Example 1 except that the same amount of a 5 poise epoxy equivalent 195 cresol novolak type epoxy resin was used, and this powder was subjected to room temperature compression molding with a tableting machine. , Sectional diameter 9.8 mm, height 1
A cylindrical resin tablet having a weight of 4.2 mm and a weight of 1.75 g was manufactured. The melt viscosity of this tablet at 175 ° C is 5
At 70 poises, the tableting density was 90%. This tablet was used as a semiconductor encapsulating resin tablet of the present invention.

Comparative Example 1 Instead of the epoxy resin A, the melt viscosity at 150 ° C. was 5
An epoxy resin composition powder was obtained in the same manner as in Example 1 except that the same amount of the epoxy equivalent of Poise's epoxy equivalent of 195 was used for the cresol-novolak type epoxy resin and the amount of the silicon dioxide powder was changed to 75 parts. It was This powder was compression-molded at room temperature with a tableting machine to obtain a cross-sectional diameter of 9.8 mm and a height of 14.
A cylindrical resin tablet having a diameter of 2 mm and a weight of 1.75 g was manufactured. The melt viscosity of this tablet at 175 ° C is 120.
With poise, the tableting density was 90%. This tablet was used as a comparative semiconductor encapsulating resin tablet.

Comparative Example 2 An epoxy resin composition powder was obtained in the same manner as in Example 1 except that the amount of silicon dioxide powder used was changed to 128 parts. This powder was subjected to room temperature compression molding with a tableting machine to produce a cylindrical resin tablet having a cross-sectional diameter of 9.8 mm, a height of 14.2 mm and a weight of 1.75 g. 175 of this tablet
Melt viscosity at ℃ is 1,500 poise, tableting density is 90
It was in%. This tablet was used as a comparative semiconductor encapsulating resin tablet.

Next, using each of the resin tablets according to the above-mentioned Examples and Comparative Examples, the semiconductor was resin-sealed by runnerless transfer molding, and its performance was examined. The molding die used had the structure shown in FIG. The number of pots is 103, and therefore the number of cavities is 20, each gate has a cross-sectional area of 0.7 mm ² and a length of 7 mm, and the capacity of each cavity is 402 mm ³ .

Ten semiconductor element assembly structures are arranged at predetermined intervals on the two lead frames arranged in the molding die, and these structure are fixed so that they are located in the respective cavities. It will be done. The mold temperature is 1
The temperature was 80 ° C., the plunger pressure was 90 kg / cm ² , and the plunger speed was 1.85 mm / sec. Depending on the mold temperature, the resin tablet is usually heated to a temperature of 175 to 180 ° C.

Regarding the semiconductor device thus resin-sealed, the number of voids in the resin-sealed portion and the damage of the semiconductor device were examined, and the results are shown in Table 1 below.
The number of voids is obtained by taking a photograph with a soft X-ray device and examining the number of voids having a diameter of 0.2 mm or more. Further, the damage of the semiconductor device is examined by a soft X-ray photograph for whether or not there is an abnormality such as disconnection or bending of the bonding wire in the semiconductor element assembly structure.

[0038]

[Table 1]

As is clear from the results shown in Table 1 above, according to the resin tablet of the present invention, it is possible to manufacture a highly reliable resin-sealed semiconductor device having few voids and no damage to the semiconductor. You can

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a runnerless transfer molding die to which a resin tablet of the present invention is applied.

FIG. 2 is a plan view showing a state in which a semiconductor is sealed with a resin using the above-mentioned molding die and then released from the molding die.

3 (A) and 3 (B) are configuration diagrams showing examples in which the connection state of the pot, the gate, and the cavity are different as a modified example of the molding die of FIG.

[Explanation of symbols]

1 pot 2 (2a, 2b, 2c, 2d, 2e, 2f, 2g, 2g
', 2h, 2h') Cavity 3 (3a, 3b, 3c, 3d, 3e, 3f, 3g, 3
h) Gates 6a, 6b Semiconductor element assembly structure 7 Resin tablet 10, 11 Molding die 20a, 20b Sealing resin

Claims (4)

[Claims] 1. A molding die having a pot and a gate having one end directly connected to the pot and the other end having a semiconductor element assembly structure arranged therein, the mold being put into the pot and being inserted into the pot. -In a resin encapsulating resin tablet to be melt-pressed into the cavity through a container, which is composed of a composition containing a thermosetting resin and an inorganic filler, and at a mold temperature for the melt-pressing. Has a melt viscosity in the range of 500 to 1,000 poise and a tableting density of 90% or more. 2. The semiconductor encapsulating resin tablet according to claim 1, which has a tableting density of 93% or more. 3. The average particle size of the inorganic filler is 5 to 20.
The resin tablet for semiconductor encapsulation according to claim 1 or 2, which has a thickness of about μm. 4. The resin encapsulating resin tablet according to any one of claims 1 to 3, wherein the thermosetting resin is an epoxy resin.