JPH09270437A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to execute sealing of semiconductor for a long time by injection molding using epoxy resin sealing material. SOLUTION: The method for manufacturing a semiconductor device comprises the steps of fixedly inserting the lead frame connected with a semiconductor element and wire bonded with it or the lead connected with the element into an injection mold, injection charging epoxy resin sealing material in the mold by an injection molding machine, and curing it. In this case, the injecting pressure of the machine is set to 30 to 300kg/cm<2> of the maximum pressure at the time point of injecting the material to charge 80 to 95% of the injection amount, and then the residual material is injected to be charged at 20 to 100kg/cm<2> .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a resin-sealed semiconductor device by injection molding using an epoxy resin sealing material.

[0002]

2. Description of the Related Art Transfer molding of an epoxy resin encapsulating material has been conventionally used as a method suitable for low cost, high reliability and productivity for encapsulating semiconductor elements such as IC and LSI. In transfer molding, after the epoxy resin encapsulation material is shaped into a tablet shape, it is put into a pot inside the mold, heated and melted, and then transferred to the mold cavity by pressing with a blanker and cured. It is common.

[0003] However, in this molding method, it is premised that the epoxy resin sealing material is shaped into a tablet, so that a shaping step is required. Since the shape of the tablet varies depending on the shape and size of the molded semiconductor device, many mold devices for shaping are required. In addition, since tablet injection and heat melting are required for each molding, the molding cycle cannot be shortened to a certain time or less.Therefore, cost reduction and mass productivity are limited. There is also a risk that impurities may be mixed into the stop material. Furthermore, in the transfer molding, the runner part which is a flow path until the sealing material put into the pot flows in the mold and reaches the cavity, and the remaining cull part in the pot are completely cured. Therefore, there is a problem that reuse is impossible and a large amount of resin waste is generated in a part other than a necessary semiconductor package part.

On the other hand, as a molding of a thermosetting resin molding material containing an epoxy resin, an injection molding method has been conventionally studied. In injection molding, the epoxy resin encapsulating material is supplied into the injection molding machine in the form of powder or granules, and is injected into the mold by the screw while maintaining the molten state in the cylinder. For this reason, the step of shaping into a tablet shape is unnecessary, continuous production is possible, and the equipment and time for shaping can be omitted. Further, since the molding material in a heat-melted state is injected into the mold, the curing time can be shortened as compared with transfer molding, which is a method suitable for mass production.

However, at present, injection molding has not been put to practical use as a method for molding an epoxy resin sealing material. The reason is that the viscosity of the conventional epoxy resin sealing material increases in the molten state in a cylinder heated to 70 to 110 ° C. due to the progress of the curing reaction of the resin in the sealing material, and the viscosity increases for 5 to 10 minutes. This is because they have a property of losing fluidity, and the thermal stability of the fusion sealing material is extremely low. For this reason, injection molding at a low pressure is impossible, and molding at a high pressure is required. As a result, deformation or cutting of a bonding wire on a semiconductor element, or deterioration of electric performance due to pressurization of an internal element in a diode or the like, is caused. It has been considered that the reliability of the obtained semiconductor package is significantly impaired.

Further, when molding for cleaning the mold is interrupted for a certain period of time, the epoxy resin sealing material hardens in the cylinder and cannot be injected again, which hinders continuous production. It was pointed out that the problem could occur.

[0007]

SUMMARY OF THE INVENTION The present invention provides a method of manufacturing a semiconductor device sealed by injection molding using an epoxy resin sealing material that can be molded by a conventional transfer molding method. It is possible to perform continuous molding for a long time by controlling the temperature within a specific range, and to provide a sealing method capable of efficient mass production.

[0008]

The gist of the present invention is to fix a lead frame, to which a semiconductor element is joined and wire-bonded, or a lead wire, to which a semiconductor element is joined, to an injection molding die as an insert. A method for producing a resin-encapsulated semiconductor device by injection-filling a mold with an epoxy resin encapsulating material by an injection molding machine, and curing the injection molding machine by injecting the epoxy resin encapsulating material. The maximum pressure is 30 to 300 kg / cm ² at the time of injection filling of 80 to 95% of the amount, followed by 20 to 100 k
A method of manufacturing a semiconductor device, characterized in that the remaining sealing material is injected and filled at g / cm ² .

The epoxy resin sealing material used in the present invention usually contains an epoxy resin, a curing agent, a curing accelerator, and an inorganic filler as essential components, and has a powder or granule shape. There is no need to make a tablet as in the case of transfer molding. In addition, those having good thermal stability in the cylinder of the injection molding machine and those having particularly good fluidity in the cavity and which cure quickly are desirable. In view of these points, the composition is epoxy resin. Is a novolak type epoxy resin, an epoxy resin having a low melt viscosity such as a biphenol type epoxy resin, and particularly preferably a resin having a softening point of 50 to 80 ° C.
Phenol resins such as novolak type phenolic resin, paraxylylene-modified phenolic resin, and dicyclopentadiene-modified phenolic resin are exemplified.
Phenolic resins at -120 ° C and low in mononuclear and dinuclear components are preferred. As the curing accelerator, a diazabicycloundecene (DBU) -based compound, an organic phosphine such as triphenylphosphine, or the like is used. Particularly, a low-temperature, low-activity, large-latent substance is preferable.

Next, the injection molding method will be described. The injection molding machine is not particularly limited, such as a screw in-line type, a plunger type, and a screw plunger type, but a screw in-line type is preferable from the viewpoint of easy temperature control and uniform melting.

The present invention is characterized in that the injection pressure of the injection molding machine is controlled as follows. That is, the maximum pressure is set to 30 to 300 kg / cm ² when the epoxy resin sealing material is injected and filled at 80 to 95% of the injection amount, and then the remaining sealing material is injected and filled at the injection pressure of 20 to 100 kg / cm ² . To do. In this case, the ratio of the latter pressure to the former maximum pressure is preferably 1/4 to 1/2. If each pressure is higher than the above value, the bonding wire on the semiconductor element may be deformed or cut, or the electric performance of the internal element may be reduced in a diode or the like, while if the pressure is lower than this,
There is a risk of filling failure in the cavity. The preferable range of the maximum injection pressure is 100 to 250 kg / cm ² , and the preferable pressure of the latter is 30 to 80 kg / cm ² . Such an injection pressure is lower than that in the case of injection molding of a usual thermosetting resin material. By controlling the injection pressure to a low pressure, combined with the ease of temperature control, a long-term continuous operation at a low pressure becomes possible. By molding at a low pressure, the reliability of the performance can be obtained because the pressure on the lead frame bonded with the semiconductor element that is the insert and wire-bonded or the lead wire bonded with the semiconductor element is small. Further, since the injection conditions are controlled to be constant, it is possible to prevent the occurrence of burrs and defective filling by setting appropriate injection conditions.

After fixing the lead frame or the lead wire to which the semiconductor element is bonded to the mold as an insert, and closing the mold, the sealing material is injected and filled. From the start of filling to the maximum injection pressure, it is almost constant. Filled at speed. If the maximum pressure is set at the time when the filling is continued and almost 100% is filled, the pressure directly reaches the molding portion at the last point of the filling even if the maximum pressure value is small. Alternatively, in the case of a diode or the like, there is a possibility that the electrical performance may be deteriorated due to the pressure applied to the internal element. As described above, by lowering the injection pressure shortly before the filling is completed and then filling it at a lower pressure, it is possible to prevent the modification of the bonding wire and the deterioration of the electrical performance due to the pressure applied to the internal element. .

The cylinder set temperature is usually 65 to 11
The temperature is 0 ° C, and temperature control is easy in this range, but 70 to 90 ° C is preferable from the viewpoint of melt viscosity and thermal stability. When the cylinder temperature is low, the melt viscosity of the sealing material is high, but the thermal stability is good. In the case of the epoxy resin sealing material of the present invention, particularly when the above preferred composition is used, the melt viscosity is low, so that the temperature can be set at a considerably low temperature. However, when the temperature is lower than 65 ° C., temperature control becomes difficult. On the other hand, if the temperature is higher than 110 ° C,
The melt viscosity becomes low, normal injection molding may become difficult, and thermal stability is often insufficient.

In the sealing method of the present invention, the set temperature of the mold is 150 to 190 ° C., preferably 165 to 185 ° C., depending on the curing time of the sealing material. At such a temperature, the molding cycle can be 150 seconds or less, and in the case of a sealing material having a preferable composition, 80 seconds or less.

[0015]

Embodiments of the present invention will be described below. As an epoxy resin encapsulating material, ortho-cresol novolak type epoxy resin (epoxy equivalent 200), phenol novolak (hydroxyl equivalent 103), diazabicycloundecene compound (curing accelerator) and fused silica as main components, and other mold release A material containing an agent, a pigment and the like was used.

As the injection molding machine, M-32 (screw in-line type) manufactured by Meiki Seisakusho Co., Ltd. is used, and the most nozzle side zone of the heating cylinder is 30% of the total length of the cylinder and the temperature is 75 ° C.
The temperature was set to 30 ° C. for the other parts. Regarding the injection pressure, the maximum pressure is set to 200 kg / cm ² , the time until the maximum pressure is reached after the start of injection is set to 20 seconds, and the pressure after that is set to 50 kg / cm ^2, and after maintaining this state for 5 seconds, the gate is It was decided to activate the cut pin to shut off the gate. The time from mold closing to mold opening is 60
Seconds, the total molding cycle was 80 seconds. Mold temperature is 175
Set to ° C. 20 dies were taken, IC elements (16 pDIP) were joined, and two consecutive 10 leadframes bonded with a gold wire were automatically set in the die and continuously molded. The appearance, filling property, and
The wire sweep and the surface hardness were measured. Table 1 shows the results every 5 hours.

[0017]

[Table 1]

(Measurement Method) (1) Appearance and Fillability: Visual observation, and appearance was particularly good or bad for gloss. (2) Wire sweep: The molded product was irradiated with soft X-rays, and the flow rate of the bonding wire (25 μm diameter: semi-hard gold wire with a length of 3 mm) was measured. Distance between bonds (5
The ratio of the maximum wire flow amount with respect to 00 μm) was expressed in%. (3) Surface hardness: The surface hardness of the molded product immediately after mold opening was measured with a Bacol hardness meter (# 935).

These results are equivalent to those obtained by the conventional low-pressure transfer molding, and show that there is no problem at all. Therefore, it can be seen that long-time continuous molding is possible.

[0020]

According to the present invention, semiconductor encapsulation with an epoxy resin encapsulating material can be continuously performed by injection molding for a long time without any problem. In the present invention, injection pressure control,
Particularly, by controlling to a specific low pressure, more stable continuous molding is possible. In the low-pressure molding, reliability is obtained in terms of performance because the pressure applied to the lead frame bonded with the semiconductor element that is the insert and bonded with the wire or the lead wire bonded with the semiconductor element is small.
Further, since the injection amount is controlled to be constant, it is possible to prevent the occurrence of burrs and defective filling by setting an appropriate injection amount. Further, by adopting a gate cut method in the mold before opening the mold, the lead frame can be easily transferred and post-processed.

Claims (3)

[Claims] 1. A lead frame, to which a semiconductor element is joined and wire-bonded, or a lead wire, to which a semiconductor element is joined, is fixed as an insert in an injection molding die,
A method for producing a resin-encapsulated semiconductor device by injection-filling an epoxy resin encapsulating material into the mold with an injection molding machine and curing the method, wherein the injection pressure of the injection molding machine is controlled by the epoxy resin encapsulating material. Of 80 to 95% of the injection amount, the maximum pressure is set to 30 to 300 kg / cm ^2, and then the remaining sealing material is injected and filled at ²⁰ to 100 kg / cm ² of the semiconductor device. Production method. 2. The method of manufacturing a semiconductor device according to claim 1, wherein during injection molding, after the sealing material is injected, the gate is shut off before opening the mold. 3. The cylinder setting temperature of the injection molding machine is 65.
The method for manufacturing a semiconductor device according to claim 1, wherein the temperature is ˜110 ° C. 4.