JPS61115342A - Resin tablet for sealing semiconductor - Google Patents

Abstract

PURPOSE:To obtain a semiconductor device, voids in a sealing resin thereof are reduced and which has excellent damp-proofing, reliability, etc., by constituting a resin tablet by a composition containing a thermo-setting resin and inorganic fillers and keeping melting viscosity at the temperature of a mold for melting and press-in within a specific range. CONSTITUTION:A resin tablet is constituted by a composition containing a thermo-setting resin and inorganic fillers, and melting viscosity at the temperature of a mold for melting and press-in is kept within a range of 500-1,000 poise. When melting viscosity is set within such a viscosity range, the roll-in of air at a time when the composition is charged into a pot and melted and pressed into a cavity through a gate is inhibited, thus hardly generating voids in a sealing resin cured so as to coat a semiconductor element built-up structure, which is melted and pressed into the cavity and arranged in the cavity. There is no possibility of which fluid resistance applied to the semiconductor element built-up structure at a time when the composition is melted and pressed into the cavity increases to excess, thus resulting in no possibility of physical damages against the structure.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a resin tablet for semiconductor encapsulation, which is used to encapsulate a semiconductor with a resin by a runnerless method (also referred to as a multi-plunger method), which is a type of transfer molding. .

[Prior Art] Conventional transfer molding for resin-sealing semiconductors involves a pot equipped with a plunger, a large number of launches extending radially from the pot, and a large number of launches communicating with each runner via a gate. Using a molding mold having a cavity, one semiconductor element assembly structure is placed in each cavity of the mold, and a resin tablet is placed in the pot, which is melted by the heat of the mold. By applying pressure with a plunger, the material is melted and press-fitted into each cavity via the launch and gate.

However, this molding method has the disadvantage that the resin put into the pot remains in the pot and each gate, as well as in a long and wide cross-sectional area lunch, resulting in a very large resin loss after molding.

In contrast, in recent years, runner-less transfer molding has been developed, in which multiple pots are equipped with plungers, and the sealing resin injected into each pot is passed through a gate directly to each cavity without going through a runner. Attempts have been made to encapsulate semiconductors with resin using molding molds for melting and press-fitting (see FIG. 1). This molding method has no resin loss caused by the runners as in the conventional method, so
This has the advantage of significantly reducing material costs.

However, in such a runnerless molding method, air bubbles (hereinafter referred to as voids) occur inside the sealing resin.
This tends to occur, which causes a decrease in the moisture resistance reliability of the semiconductor device and a decrease in mechanical strength.

[Problems to be Solved by the Invention] This invention solves the above-mentioned problems in runnerless transfer molding, which is much more advantageous in terms of material costs, and reduces voids inside the sealing resin. The purpose of the present invention is to obtain a semiconductor device having excellent humidity resistance and reliability.

[Means for Solving the Problems] As a result of intensive studies to solve the above problems, the inventors found that in runnerless transfer molding, the melt viscosity of the resin tablet used for this is lower than that of the semiconductor element assembly structure. In addition to the occurrence of defective products such as disconnection of bonding wires, it also greatly affects the generation of voids inside the sealing resin.When the melt viscosity is set within a specific range, the number of voids is small (and the occurrence of defective products as described above) is greatly affected. After learning that it was possible to obtain a highly reliable semiconductor device that would not cause damage, he completed this invention.

That is, the present invention has a pot and a gate that has one end directly connected to the pot and the other end directly connected to a cavity in which a semiconductor element assembly structure is arranged, that is, a runnerless mold. Has the above-mentioned kya been through the above-mentioned gate? '1 The resin tablet for semiconductor encapsulation to be melt-press-fitted into the tee is composed of a composition containing a thermosetting resin and an inorganic filler, and has a melt viscosity of 50 at the mold temperature of the melt-press-fit chamber.゛0～1,00
This invention relates to a resin tablet for semiconductor encapsulation characterized by having a poise in the range of 0 poise.

In addition, in this specification, the melt viscosity of the resin tablet refers to the cross-sectional diameter of the composition 2y constituting the tablet.
This molded sample was then molded into a tablet with a height of 15 rluR), and this molded sample was used in a Shimadzu Koka type flow tester (nozzle diameter 1, nozzle length 10, load 10 h/
cd) means the value measured at a predetermined temperature (mold temperature).

[Structure and operation of the invention]

The composition for molding resin tablets used in this invention has a thermosetting resin and an inorganic filler as essential components, and usually contains a curing agent and a curing accelerator depending on the type of thermosetting resin. Furthermore, additives such as a silane coupling agent, a mold release agent, and a coloring agent are added as necessary and mixed with or without heating.

By pulverizing this composition to a size with an average particle diameter of about 01 to 0.5, and compression molding it at room temperature according to a conventional method,
The resin tablet is made of a general type suitable for runnerless transfer molding, and has a cross-sectional diameter of 4.5 to 25 mm and a height of about 5 to 30 mm. It may be in the form of The resin tablets can also be obtained by melt-extruding the composition using an extruder and then cutting the composition into the sizes described above.

In this invention, the melt viscosity of such a resin tablet is determined by adjusting the molding mold temperature (usually 150 to 200°C) as described above.
°C, preferably 160-190 °C) at 500-i,
A major feature is that it is set within the range of o o o poise. In other words, when the viscosity is set to such a range, the entrainment of air is suppressed when the material is put into the pot and melted and press-fitted into the cavity through the gate, so that the material is melted and press-fitted into the cavity and placed here. Voids occur inside the hardened sealing resin that covers the semiconductor element assembly structure.

It will almost never be recognized. Moreover, in the above viscosity range,
Since there is no possibility that the fluid resistance applied to the semiconductor element assembly structure becomes too large when it is molten and press-fitted into the cavity, there is no particular fear of causing physical damage to the structure.

On the other hand, in conventional resin tablets, the melt viscosity is usually set to a low value of 200 poise or less from the viewpoint of melt-intrusion properties, so it is impossible to avoid entrainment of air when putting it into the pot, and this is caused by the sealing resin. This is thought to be the cause of frequent voids. As the melt viscosity is increased, the above problem will be reduced, but if it is less than 500 poise, satisfactory results cannot be obtained.On the other hand, if the melt viscosity is made too high, If the value exceeds 1,000 poise, which is outside the specified range, the fluid resistance will become thick (which may cause breakage of the bonding wire in the semiconductor element assembly structure or bending of the gold wire connecting the external lead and the semiconductor element). hand(
In some cases, the fatal defect of short circuit failure cannot be avoided.

Setting the resin tablet of the present invention within the above-mentioned specific range can be easily done, for example, by 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, and the melt viscosity of this epoxy resin is generally 1 at a temperature of 150°C, taking into account the mold temperature.
It is preferably in the range of 5 to 30 poise. Further, the melt viscosity of the tablet increases as the amount of the inorganic filler increases, but it is generally preferable that the tablet accounts for 72 to 80% by weight of the composition. Note that the melt viscosity of the epoxy resin means a value measured with an Oswald viscometer.

Such an epoxy resin has an epoxy equivalent of 17
5 to 300 cresol novolac type epoxy resins and halogenated phenol/borac type ""+' resins are preferably used. Examples include cresol novolak resins, phenolic/borac-type phenolic resins such as phenol/borac resins, etc. Also, curing accelerators commonly used with these curing agents include 2-methylimidazole, boron trifluoride, triphenyl Examples include phosphine.

Further, as the above-mentioned inorganic filler, quartz glass powder,
Silicon dioxide powder etc. are preferably used, but other conventionally known calcium silicate, aluminum nitride, zircon oxide, clay, calcium carbonate, antimony oxide,
It is also possible to use powders such as alumina, silicon carbide, glass fibers, etc.

The average particle size of this inorganic filler is generally 5 to 20
It is desirable that it be about fi1n.

The resin tablet of the present invention is characterized by having a melt viscosity within a specific range as described above. Molding density (hereinafter referred to as tableting density)
It is preferably 90% or more, preferably 93% or more. If the tableting density becomes too low, the amount of air contained when the tablet is added to the pot increases, which may impair the effect of reducing voids by regulating the melt viscosity.

In addition, the above-mentioned tablet density is [tablet density (y/er
V)/cured resin density (y/crtl) ]X 100
The tablet density is expressed as the weight of the tablet (FA/capacity of the tablet (cII)), and the density of the cured resin is expressed as the weight of the cured resin (b)/the capacity of the cured resin (d). Each of these is required.

Next, a method for resin-sealing a semiconductor by runnerless transfer molding using the resin tablet of the present invention will be described with reference to FIGS. 1 to 3.

FIG. 1 shows the cross-sectional structure of a runnerless transfer molding mold consisting of an upper mold 10 and a lower mold 11, and shows a plurality of pots 1 arranged in series at predetermined intervals in the direction perpendicular to the plane of the drawing, and each of these pots 1. Gates 3 (3a, 3) have one end directly connected to pot 1 and the other end directly connected to cavity 2 (2a, 2b).
b), and each pot 1 has a plunger 4.
is installed.

The size of each component described above varies depending on the size of the semiconductor to be resin-sealed, but for example, the pot 1 is designed to have a shape and size corresponding to the resin tablet 7, and the gate 3 has a cross-sectional area that is normally It is designed so that the length is generally 5 to 15 mm. Note that this size is almost the same even when other molding molds as shown in FIGS.

In the cavities 2a and 2b of such a mold,
Semiconductor element assembly structures 6a and 6b (for example, 16-Pin DIP, 4
The resin tablet 7 of the present invention is placed in each pot 1, and is pressurized by the plunger 4 while being heated at the mold temperature. As mentioned above, the mold temperature at this time is usually 150 to 200°C, preferably 160°C.
~190°C, and the plunger pressure is typically 50-1
20 KFI/c11i, preferably 70-100Kf
/cr! It is said that

The resin tablet 7 is melted by the heating and pressurization described above and is press-fitted into the cavities 2a, 2b through the gates 3a, 3b, where it hardens while completely covering the semiconductor element assembly structures 6a, 6b disposed therein. At this time, since the melt viscosity of the resin tablet 7 is within the above-mentioned specific range, there are almost no voids in the cured resin, and there is no possibility of causing physical damage to the assembled structures 6a, 6b.

FIG. 2 shows a state in which the mold has been released from the molding die consisting of the upper mold 10 and the lower mold 11 after transfer molding as described above, and 20a and 20b are attached to lead frames 5a and 5b, respectively. This is a hardened sealing resin that covers the semiconductor element assembly structures 6a and 6b arranged at intervals. In addition, 30a and 30b are the resins hardened in each gate 3a and 3b, and 100 is the resin hardened in each pot 1. These 30a.

30b and 100 are resin parts that cause molding loss, but since there is no runner, there is no resin loss at this launch part (material cost can be reduced accordingly).

In the mold shown in FIG. 1, the cavities 2a and 2b are directly connected to the other ends of the gates 3a and 3b, one end of which is directly connected to one pot 1, respectively. The number of cavities 2 directly connected to the pot 1 via the gate 3 can be freely selected in the range of generally 1 to 6, preferably 2 to 4. For example, FIG. 3 (031) shows an example of this.

That is, as shown in FIG. 3(5), a configuration may be adopted in which four cavities 2c, 2d, 2e, and 2f are directly connected to one pot 1 via gates 3c, 3d, 3e, and 3f ( , and as shown in Fig. 3 031, one pot 1
The gates 3g and 3h, each of which has one end directly connected to the gate, may be bifurcated, and the two cavities 2g and 2g' and 2h and 2h' may be directly connected to each end thereof.

[Effects of the Invention] As described above, in this invention, by setting the melt viscosity of the resin tablet for runnerless transfer molding within a specific range, it is possible to seal the semiconductor element assembly structure during molding without damaging it. It is possible to reduce voids inside the sealing resin, thereby making it possible to obtain a resin-sealed semiconductor device with excellent moisture resistance and reliability.

[Examples] Below, examples of the present invention will be described in more detail. In addition, in the following, parts shall mean parts by weight.

Example 1 Epoxy equivalent weight 1 with a melt viscosity of 25 poise at 150°C
95 cresol novolac type epoxy resin (hereinafter referred to as epoxy resin A) 20 parts, novolac type phenol resin 10 parts, silicon dioxide powder bundle 96 parts, 2-methylimidazole 0.5 part, carnauba wax 0.5 part, carbon 0.5 part of black and 0.5 part of silane coupling agent
After heating and kneading for 5 minutes using heated rolls at 90°C, the mixture was cooled and ground to obtain an epoxy resin composition powder having an average particle size of 0.1 to 0.5.

This powder was compression-molded at room temperature using a tablet machine, and the cross-sectional diameter was 9.
A cylindrical resin tablet having a length of 8 rug, a height of 13 cm and a weight of 1.77 y was manufactured. 175° of this tablet
The melt viscosity at C was 800 poise and the tablet density was 95%. This tablet was used as a resin tablet for semiconductor encapsulation of the present invention.

Example 2 The epoxy resin composition powder prepared in Example 1 was compression molded at room temperature using a tablet machine, and the cross-sectional diameter was 9.8 tm and the height was 14 mm.
．． A cylindrical resin tablet having a weight of 2ag+ and a weight of 1.75y was manufactured. The melt viscosity of this tablet at 175°C was 805 poise, and the tablet density was 90%. This tablet was used as a resin tablet for semiconductor encapsulation of the present invention.

Example 3 Instead of 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 Talesol novolac type epoxy resin with a 5 poise epoxy equivalent of 195 was used, and this powder was compression molded at room temperature using a tablet machine. Cross-sectional diameter: 9.8 mm, height: 14 mm.
A cylindrical resin tablet measuring 2M and weighing 1.75y was manufactured. The melt viscosity of this tablet at 175°C is 57
The tablet density was 90%. This tablet was used as a resin tablet for semiconductor encapsulation of the present invention.

Comparative Example 1 Instead of 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 Poise's cresol novolac type epoxy resin having an epoxy equivalent of 195 was used, and the amount of silicon dioxide powder used was changed to 75 parts. . This powder was compressed at room temperature using a tablet machine, and the cross-sectional diameter was 9.8 rxx and the height was 1.
4.2 So-called 2 weight 1.75? A cylindrical resin tablet was manufactured. The melt viscosity of this tablet at 175°C was 120 poise, and the tablet density was 90%. This tablet was used as a semiconductor encapsulation resin tablet for comparison.

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 compression molded at room temperature using a tablet machine, and the cross-sectional diameter was 9.
．． A cylindrical resin tablet with a length of 8 m, a height of 14.2+tw, and a weight of 1.75 y was manufactured.

The melt viscosity of this tablet at 175° C. was 1,500 poise, and the tablet density was 90%. This tablet was used as a semiconductor encapsulation resin tablet for comparison.

Next, using each of the resin tablets according to the above Examples and Comparative Examples, a semiconductor was resin-encapsulated by runnerless transfer molding, and its performance was investigated. A mold having the structure shown in FIG. 1 was used. The number of pots is 103,
Therefore, the number of cavities is 20, each gate has a cross-sectional area of 0.7 and a length of 7III11, and the capacitance of each cavity is 402 at3. Ten semiconductor element assembly structures are arranged at predetermined intervals on each of the two lead frames disposed in this molding die, and these structures are fixed so as to be positioned within each cavity. The mold temperature is iso'c1, the plunger pressure is 90Kg/c++f, and the plunger speed is 1.851.
m/sec. Depending on the above-mentioned mold temperature, the resin tablet is usually heated to a temperature of 175 to 180°C.

The results of investigating the number of voids in the resin-sealed portion of the semiconductor device resin-sealed in this way and damage to the semiconductor device are as shown in the table below. In addition, the number of voids is soft
Photographs were taken using a wire device, and the number of voids with a diameter of 0.2 mm or more was determined. In addition, damage to the semiconductor device was examined using soft xN photography to determine whether abnormalities such as disconnection of bonding wires or bending of gold wires in the semiconductor element assembly were observed.

As is clear from the above results, according to the resin tablet of the present invention, a highly reliable resin-sealed semiconductor device with few voids and no damage to the semiconductor can be manufactured.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing an example of a runnerless transfer molding mold to which the resin tablet of the present invention is applied, and Fig. 2 is a sectional view showing an example of a runnerless transfer molding mold to which the resin tablet of the present invention is applied. A plan view showing a state in which the mold has been released from the mold, and FIGS. 3(A) and 3(B) are configuration diagrams showing a modified example of the molding mold shown in FIG. 1 in which the connection state of the pot, gate, and cavity is different. It is. 1... Pot, 2 (2a, 2b, 2c, 2d, 2e,
2f. 2g, 2g', 2h, 2h') - cavity, 3 (3a
, 3b. 3 c + 3 d r 3 e + 3 f t 3
g + 3 h)...Gate, 6a, 6b...
・Semiconductor element assembly structure, 7...Resin tablet, 10
, 11...molding mold, 20a, 2Qb-=sealing resin

Claims (3)

[Claims] (1) It is placed in the pot of a molding mold having a pot and a gate, one end of which is directly connected to the pot and the other end of which is directly connected to a cavity in which a semiconductor element assembly structure is arranged, and the above-mentioned A resin tablet for semiconductor encapsulation that is melt-press-fitted into a cavity is composed of a composition containing a thermosetting resin and an inorganic filler, and has a melt viscosity of 500 to 500 at the mold temperature for melt-press-fitting. 1,
1. A resin tablet for semiconductor encapsulation, characterized in that it is in the range of 0,000 poise. (2) The resin tablet for semiconductor encapsulation according to claim (1), wherein the thermosetting resin is an epoxy resin. (3) The resin tablet for semiconductor encapsulation according to claim (1) or (2), in which the inorganic filler accounts for 72 to 80% by weight in the composition.