JPH05308087A - Semiconductor resin sealing device - Google Patents

Abstract

PURPOSE:To improve quality by preventing void from being generated by making uniform flow speed of a melted resin which is supplied within a cavity without changing a basic dimensional configuration for storing a semiconductor element into a cavity. CONSTITUTION:A cavity K is formed between an upper mold 10 and a lower mold 11, a semiconductor element c is placed on a lead frame a and a die pad b to be sealed with resin and at the same time is stored while being connected via a lead within the cavity, a melted sealing resin material is supplied to the cavity K for sealing the semiconductor element c with resin, and then upper and lower molds are provided with heaters which are means for setting mutually different temperatures.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor resin sealing device.

[0002]

2. Description of the Related Art As shown in FIG. 7, a semiconductor device S includes a lead frame a, a semiconductor element c mounted on a die pad b integral with the lead frame a, and a lead frame a and a semiconductor element c. Are connected via a lead d such as a gold wire. The lead frame a and the semiconductor element c together with the lead d are sealed with a resin while leaving the outer lead portion a1 which is the outer end of the lead frame a. A thermosetting resin is usually used as the resin material for the resin sealing, and is, for example, an epoxy resin material.

Although such a semiconductor device is used in a wide variety of products, in any case, since there is a great demand for promoting miniaturization of the product, the semiconductor device S itself is of a thin type. There is.

In the case of the semiconductor device shown in the same figure, even if the longitudinal dimension W of the resin-sealed package portion G is about 17 mm, the thickness dimension e is only 1 to 1.5 mm. The resin thickness dimension f in the upper surface portion of the semiconductor element c is about 270 μm, while the resin thickness dimension h in the lower surface portion of the die pad b is about 170 μm.

The resin encapsulation for obtaining such a semiconductor device S is performed by accommodating the semiconductor element c and the like having the above structure in a space called a cavity formed in the mating surface of the upper mold and the lower mold. The molten sealing resin material is supplied into the cavity.

The upper and lower molds are heated, and the molten resin material is filled in the cavity and further heated to cure. After the required curing temperature and the required curing time have elapsed, the heating of the mold is stopped and the mold is cooled. After a lapse of a predetermined time, the upper and lower molds are separated and the resin-sealed semiconductor device is taken out.

[0007]

In order to obtain a high quality resin-sealed semiconductor device, the molten resin supplied into the cavity must be made to flow uniformly.

In some cases, voids, which are air pockets, may be created during resin sealing. When this is used in an actual product, the air accumulated in the void and the water contained therein vaporize and expand to generate stress when the ambient temperature around the product rises, and finally cracks occur in the sealing resin part. As a result, the set function cannot be obtained. The mechanism of generation of such a void is shown in FIG.

As shown in the uppermost part of the figure, the molten resin J supplied from the gate i into the cavity K passes through the space between the lead frame a and the die pad b, and the upper surface space of the semiconductor element c. m or flow to the lower surface space n of the die pad b.

Hereinafter, in order, the cross-sectional area of the semiconductor element upper surface space m is larger than the cross-sectional area of the die pad lower surface space n, the flowability of the sealing resin J is good, and the molten resin J supplied from the gate i. Since the viscosity of C is the same in the cavity K, the flow velocity of the molten resin J in the upper surface space m of the semiconductor element is faster than that in the lower space n of the die pad.

Therefore, this portion is completely filled first, and then the molten resin J advances into the space n of the lower surface of the die pad. Here, the molten resin J directly faces the die pad lower surface space n, but when the unavoidable conditions such as the difference in the flow velocity at each portion and the temperature difference between the respective flow tip portions overlap, A void P is generated at the facing portion.

If the cross-sectional area of the upper surface space m of the semiconductor element and the cross-sectional area of the lower surface space n of the die pad are made the same, the generation of the void P can be suppressed, but the lead frame a and the semiconductor element c are wire-bonded. Due to this, the above dimensions cannot be changed.

Another factor causing the void P is the viscosity of the resin. That is, as a characteristic of the thermosetting resin, the higher the temperature of the resin itself, the lower the viscosity and the easier it is to flow. On the other hand, when the temperature of the resin is low, the viscosity is high and the resin is hard to flow.

As shown in FIG. 9, the initial lead frame a, die pad b, and semiconductor element c housed in the cavity K are lower than the temperatures of the upper die 1 and the lower die 2 themselves.

Therefore, the molten resin J flowing from the gate i into the cavity K is cooled by the lead frame a, etc., and its temperature is lowered and its viscosity is increased. That is, the fluidity of the molten resin J deteriorates.

The cavity K formed by the upper mold 1
Than the cross-sectional area of the upper surface space m of the semiconductor element c inside
The die pad b inside the cavity K formed by the lower mold 2.
Since the cross-sectional area of the lower surface space n is smaller, the molten resin J flowing in the lower space n of the die pad b is further cooled, and the fluidity is further deteriorated. Therefore, it becomes a factor of generating void P.

Further, in such a semiconductor resin sealing device, it is usual that a plurality of cavities are provided and the molten resin is guided at the same time to perform resin sealing. Therefore, the cause of the generation of the void P must be considered not only in the individual cavities but also as a problem of the entire device.

As shown in FIG. 10, the resin is accommodated in the pot 3 in a molten state. A runner 4, which is a flow path for the molten resin, is connected to the pot 3. A plurality of gates 5 ... Are provided in the runner 4, and the cavities K ₁ and K are respectively branched to these gates 5.
₂ ... communicate.

Actually, in the state where the molten resin is supplied from the pot 3, the supply pressure is high and the position is closest to the pot 3, that is, the cavity K on the most upstream side of the runner 4.
Inflow pressure to ₁ is high.

However, the pressure of the molten resin decreases while flowing through the runner 4, and the inflow pressure decreases as it flows into the downstream cavities K ₅ ...

Due to such a difference in the inflow pressure, the time required until the molten resin is completely filled is different although the cavities K ₁ , K _2, ... Have the same capacity. As a result, it is difficult to obtain the same quality, and void P may be generated in some cases.

The present invention has been made in view of the above circumstances, and its first object is to accommodate a semiconductor element in a cavity without changing the dimensional basic structure. (EN) A semiconductor resin encapsulation device capable of achieving uniform flow rate of a supplied molten resin, preventing generation of voids, and improving quality.

A second object is to make the filling time uniform in all the cavities in consideration of the fluidity of the molten resin in the entire apparatus having a plurality of cavities, and to obtain the resin sealing quality obtained. The present invention provides a semiconductor resin encapsulation device that leads to improvement of

[0024]

In order to achieve the above object, the first invention is to form a cavity between an upper die and a lower die, and to provide a lead frame and resin to be sealed in the cavity. A semiconductor resin encapsulation device for accommodating a semiconductor element mounted on a die pad and connected to a lead frame via a lead, and supplying a molten encapsulating resin material to the cavity to perform resin encapsulation of the semiconductor element. 2. A semiconductor resin encapsulating apparatus, characterized in that it comprises means for setting the upper mold and the lower mold to temperatures different from each other.

A second aspect of the present invention is a heating body which is provided in each mold as a means for setting the upper mold and the lower mold at different temperatures, and which controls heating of the molds at different temperatures. As a third invention, the upper die and the lower die are
As means for setting different temperatures, the respective molds are made of materials having different thermal conductivities.

In a fourth aspect of the present invention, a plurality of cavities are formed in a mold, and a semiconductor element mounted on a lead frame and a die pad to be resin-sealed and connected to the lead frame via leads is used for each cavity. Housed inside,
In a semiconductor resin encapsulation device for encapsulating a semiconductor element by simultaneously supplying a molten encapsulating resin material from a pot to a plurality of cavities via a runner, a mold part in the vicinity of the pot is separated from the pot. It is a semiconductor resin encapsulation apparatus characterized in that it is provided with means for setting the temperature of the mold part to be different from each other.

[0027]

In the first to third aspects of the present invention, by controlling the upper mold and the lower mold at different temperatures from each other, the flow rate of the molten resin flowing through the mold spaces forming the cavity is controlled. Homogenize.

In the fourth aspect of the present invention, since the resin sealing molding temperature is changed between the portion near the pot of the mold and the portion separated from the pot, the temperature of the molten resin when being introduced into each cavity is set to the temperature of each cavity. To homogenize.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings, and a completed semiconductor device S as shown in FIG. 7 can be obtained. First, an embodiment of the first invention will be described.

As shown in FIG. 1, an upper die 10 and a lower die 1
1. A semiconductor element c mounted on a die pad b and a lead frame a connected to this semiconductor element c by a wire bonding means are provided in a cavity K which is composed of 1 and has the same dimension as the conventional one. Be accommodated. The dimensional configuration of the semiconductor device c and the like with respect to the cavity K is
It is completely the same as the conventional one described above.

A first heater 12, which is a heating body, is embedded in a predetermined portion of the upper mold 10. The heater 12 has a heat generating capacity for heating and retaining the upper mold 10 at a predetermined temperature. The heater 12 is used as the upper mold 1.
0 upper mold 1 through temperature controller 13 arranged outside
It is electrically connected to the temperature sensor 14 provided in the vicinity of the zero cavity K.

The temperature sensor 14 detects the temperature of the upper mold 10, especially in the vicinity of the cavity K, sends a detection signal to the temperature controller 13, compares it with a preset temperature, and responds to the temperature difference. The heat generation capacity of the heater 12 can be controlled so as to reach the temperature.

On the other hand, a second heater 15 which is a heating body is embedded in a predetermined portion of the lower mold 11. The heater 15 has a heat generating capacity for heating and keeping the lower mold 11 at a predetermined temperature. The heater 15 is provided with a temperature sensor 1 provided near the cavity K of the lower mold 11 via a temperature controller 16 arranged outside the lower mold 11.
7 electrically connected.

The temperature sensor 17 detects the temperature of the lower die 11, especially in the vicinity of the cavity K, sends a detection signal to the temperature controller 16, compares it with a preset temperature, and responds to the temperature difference. The heat generation capacity of the heater 15 can be controlled to reach the temperature.

The upper and lower molds 10 and 11 are preferably made of a material having a high thermal conductivity in order to embed the heaters 12 and 15, respectively. For example,
Aluminum alloy material and copper alloy material are most suitable.

A molten thermosetting encapsulating resin (not shown here), such as an epoxy resin, flows into the cavity K from the gate i to encapsulate the semiconductor element c and the like disposed therein. ..

More specifically, the molten resin flowing from the gate i into the cavity K flows along the lower portion of the lead frame a, and further the space m of the upper surface of the semiconductor element through the space between the lead frame a and the die pad b. And those flowing directly into the die pad lower surface space n.

The first and second heaters 12 and 15 generate heat, and heat the respective molds 10 and 11. Therefore, the inside of the cavity K is heated and the fluidity of the molten resin introduced therein is good.

However, by utilizing the characteristics of this thermosetting resin, the heating set temperature of the first heater 12 is lowered and
The temperature controllers 13 and 16 are stored so as to raise the heating set temperature of the heater 15.

As a result, the flow rate of the molten resin introduced into the upper surface space m of the semiconductor element becomes slower and the flow rate of the molten resin introduced into the lower space n of the die pad becomes faster.
Despite the difference in these cross-sectional areas, the molten resin is simultaneously filled in each space m, n. As a result of the improved fluidity of the molten resin, the occurrence of voids is not seen. The flow rate of the molten resin in the cavity K can be approximated by the following equation (1) using a rectangular flow rate equation. V = 1 / μβ · dP / dx (1) V: resin flow velocity, μ: resin viscosity, dP / dx: pressure gradient in the flow direction. However, β is, as shown in the equation (2),

[0041]

[Equation 1] a: 1 / the width of the package G (cavity K)
2, b: 1/2 of the thickness of the package G (cavity K). In the space m of the upper surface of the semiconductor element in the cavity K, V = V ₁ , β = β ₁ , and μ = μ ₁ ,
In the space n on the lower surface of the die pad, V = V ₂ , β =
If β ₂ and μ = μ ₂ , then β ₁ = 79.2 and β ₂ = 29
It becomes 5.0. Table 1 shows how V ₁ / V ₂ was improved in the above-described Examples by using the result calculated based on the experimental value as the resin viscosity.

[0042]

[Table 1]

In this way, by setting the heating temperature for the lower die 11 which is the second heater 15 to be higher, V ₁ / V ₂ is lowered from 3.72 to 2.55, Space m on the upper surface of the semiconductor element and space n on the lower surface of the die pad
It can be seen that the difference in the flow rate of the molten resin, that is, the difference in the filling rate, was reduced.

As shown in FIG. 2, each die 1 near the cavity K and near the mating surfaces of the upper and lower dies 10, 11.
0 and 11 have a plurality of heaters 12A ...
5A may be provided.

These heaters 12A ..., 15A ...
The temperature of each mold 10 and 11 is controlled. This temperature control is performed in the same manner as described above with reference to FIG. Therefore, the same effect is obtained. Here, the viscosity of the thermosetting resin can be defined as a function of temperature as shown in equation (3).

[0046]

[Equation 2] FIG. 4 shows a flow model of the molten resin in the space n of the lower surface of the die pad. Z of the resin flow velocity in the X direction at this time
The directional average value is expressed by equation (4).

[0047]

[Equation 3] The temperature distribution of the molten resin is

[0048]

[Equation 4] Becomes Here, when T ₀ is fixed at 150 ° C. and the relationship between the temperature of the semiconductor element c disposed in the cavity K and the flow rate of the molten resin is compared, equations (3) to (5) indicate that

[0049]

[Equation 5] Becomes

As described above, when the temperature of the semiconductor element c etc. in the cavity K is raised by 3 ° C., the flow rate of the molten resin becomes 10.
It rose by 6%. Therefore, the fluidity of the resin is improved,
It is possible to prevent unfilling in the cavity K and suppress the generation of voids.

As shown in FIG. 3, by forming auxiliary mating molds 10A and 11A made of a metal material having a high thermal conductivity, only the portions constituting the mating surfaces of the upper and lower molds 10 and 11 are formed.
The same result as when the above heater is provided is obtained, and the same effect is obtained.

As means for setting the upper and lower molds 10 and 11 at different temperatures, the respective molds 10 and 11 are previously set.
Materials having different thermal conductivities may be adopted as the materials constituting the.

That is, if the material composing the upper die 10 has a low thermal conductivity to some extent and the material composing the lower die 11 is composed of a material having a high thermal conductivity, the same as in the above embodiment. It exerts a working effect. As shown in FIG.
You may comprise a semiconductor resin sealing device.

In this case, the pot 3, the runner 4 connected to the pot 3, and a plurality of gates 5 are provided at predetermined intervals in the runner 4, and the cavities K ₁ and The fact that K ₂ ... Is connected in a branched manner is the same as in the conventional device.

However, a pair of heaters 18 and 19 are provided in the mold 30 constituting the runner 4, the gate 5 and the cavities K ₁ and K ₂ . One heater 18 is arranged near the cavity into which the molten resin introduced from the pot 3 is first introduced, that is, near the cavity K ₁ on the upstream side of the runner 4. The other heater 19
Is arranged near the cavity into which the molten resin is guided slowly, that is, near the cavity K ₅ on the downstream side of the runner 4.

Further, the respective heaters 18, 19
Is electrically connected to the temperature controllers 20 and 21,
The heat generation temperature is controlled. Each temperature controller 20, 21
Are arranged at positions not so far apart from the heaters 18 and 19 connected to them, respectively, and receive detection temperature signals from temperature sensors 22 and 23 that detect the temperature of the mold 30 part.

A preset heating temperature is stored in advance in each of the temperature controllers 20 and 21, and the heaters 18 and 19 are compared so as to compare with the detected temperature and to generate heat according to the difference.
A control signal can be sent to.

Then, the molten resin collected in the pot 3 is supplied to the runner 4, and is further guided from the runner 4 to the respective cavities K ₁ , K _2, ... Through the plurality of gates 5. By the way, the thermosetting resin which is a molten resin,
Due to its characteristics, the higher the temperature, the lower the viscosity and the easier it becomes to flow.

Utilizing this characteristic, the heating temperature of the heater 18 arranged on the upstream side of the runner 4 is set low, and the heating temperature of the heater 19 arranged on the downstream side of the runner 4 is set high.

By controlling the heating of the die 30 as described above, the flow velocity of the molten resin especially on the downstream side of the runner 4 is increased, and the cavities K ₁ and K _{2 at} any portion are increased.
Also, the time until the complete filling of the molten resin becomes the same, voids do not occur, and the same quality can be obtained. Here, the inflow amount of the molten resin flowing into the cavity K through the gate 5 can be approximated by the equation (6). Q = P / (β · η) (6)

Q: amount of resin flowing in, P: pressure at gate inlet,
β: gate shape resistance, η: resistance. If the runner upstream side P near the pot 3 and the runner downstream side E at the runner end are adopted as subscripts, the ratio of the resin amount flowing into the runner upstream side and downstream runners is: Q _P / Q _E = P _P in the case of _{· β E · η E / P} E · β P · η P ...... (7) gate 5 shape is the same, the above formula _{(7), Q P / Q E = P} P · η E / P E・ Η _P …… (8)

Table 2 shows how Q _P / Q _E was improved by adopting the structure of the above example by using the value calculated based on the experimental value as the resin viscosity. However, P _P / P _E shall be 1.2.

[0063]

[Table 2] That is, by setting the temperature of the die 30 on the runner downstream side to be high, Q _P / Q _E is decreased from 1.2 to 1.0, and the cavity K between the runner upstream side and the runner downstream side is reduced.
It can be seen that the amount of inflow resin in the inside is almost equal.

As shown in FIG. 6, the mold 30A material on the upstream side and the mold 30B material on the downstream side are changed with the central portion of the runner 4 as a boundary, whereby the operation and effect described above can be obtained. Similar results can be obtained. Naturally, the material of the runner downstream die 30B must have a higher thermal conductivity than the material of the runner upstream die material 30A. Further, various modifications can be considered within the scope of the present invention.

[0065]

As described above, according to the present invention, the upper die and the lower die are provided with means for setting the temperatures to be different from each other. There is an effect that the flow rate of the molten resin supplied in the cavity is made uniform without changing the configuration, the generation of voids is prevented, and the quality can be improved.

Further, according to the present invention, since the resin encapsulation molding temperature is changed between the portion of the mold near the pot and the portion separated from the pot, the molten resin of the entire apparatus having a plurality of cavities is changed. In consideration of fluidity, the filling time is made uniform in all the cavities, and the effect of improving the obtained resin sealing quality is achieved.

[Brief description of drawings]

FIG. 1 is a partial vertical cross-sectional view of a semiconductor resin sealing device showing an embodiment of the present invention.

FIG. 2 is a partial vertical cross-sectional view of a semiconductor resin sealing device according to another embodiment.

FIG. 3 is a partial vertical cross-sectional view of a semiconductor resin sealing device of still another embodiment.

FIG. 4 is a diagram schematically showing flow characteristics of another example.

FIG. 5 is a diagram showing a schematic configuration of a semiconductor resin encapsulation device of still another embodiment.

FIG. 6 is a diagram showing a schematic configuration of a semiconductor resin encapsulation device of still another embodiment.

FIG. 7 is a vertical cross-sectional view of the completed semiconductor device.

FIG. 8 is a diagram illustrating a mechanism of void generation during resin sealing.

FIG. 9 is a partial vertical cross-sectional view of a semiconductor resin sealing device of a conventional example.

FIG. 10 is a diagram showing a schematic configuration of a semiconductor resin encapsulation device of a conventional example.

[Explanation of symbols]

10 ... Upper mold, 11 ... Lower mold, K ... Cavity, a ... Lead frame, b ... Die pad, c ... Semiconductor element, 1
2, 15 ... Heating body (heating heater), 3 ... Pot, 4 ... Runner.

Claims (4)

[Claims] 1. A cavity is formed between an upper die and a lower die, and the cavity is mounted on a lead frame and a die pad to be resin-sealed in the cavity and is connected to the lead frame via a lead. In a semiconductor resin encapsulation device that accommodates a semiconductor element and supplies a molten encapsulating resin material to the cavity to encapsulate the semiconductor element, the upper die and the lower die are set to different temperatures. A semiconductor resin encapsulation device comprising means. 2. The means for setting the upper mold and the lower mold at different temperatures from each other is a heating body provided in each mold and heating and controlling the molds at different temperatures. The semiconductor resin sealing device according to claim 1. 3. The means for setting the upper mold and the lower mold at different temperatures from each other, the respective molds are made of materials having different thermal conductivities. Semiconductor resin sealing device. 4. A plurality of cavities are formed in a mold, and a semiconductor element mounted on a lead frame and a die pad to be resin-sealed and connected to the lead frame via leads is housed in each cavity. In a semiconductor resin encapsulation apparatus for encapsulating a semiconductor element by simultaneously supplying a molten encapsulation resin material from a pot to a plurality of cavities via a runner, a mold part near the pot and a part separated from the pot A semiconductor resin encapsulating apparatus, characterized in that it comprises means for setting the temperature of the die part to different temperatures.