JP2011049442A - Semiconductor device and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device in which a semiconductor element is resin-sealed by transfer molding using an epoxy resin sealing material, and to provide a method of manufacturing the semiconductor device. <P>SOLUTION: A lead frame and a lead wire to which the semiconductor element is jointed are fixed to a transfer mold, and the epoxy resin-sealing material is pressed, filled and cured to the transfer mold by a transfer molding machine, and thereby, the semiconductor element is resin-sealed. When the semiconductor element is transfer-molded with an epoxy resin, the epoxy resin is injected at a first molding temperature and a first molding time, and then, the epoxy resin is cured at a second molding temperature higher than the first molding temperature and a second molding time. After maintaining the first holding temperature at 150&deg;C and the first molding time for 20 seconds, the second molding temperature which was preset is automatically increased to be 175&deg;C and the second molding time is maintained for 10 seconds. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a semiconductor device and a manufacturing method thereof, and more particularly to a semiconductor device in which a semiconductor element is resin-sealed by transfer molding using an epoxy resin sealing material and a manufacturing method thereof.

  Conventionally, a semiconductor device is generally resin-sealed by a transfer molding method using an epoxy resin or the like. The semiconductor device is electrically connected to an external lead by wire bonding using a gold wire or the like. It is known that wire deformation occurs in some cases in a process using a combination of such a transfer molding method and a wire bonding method.

  In transfer molding, an epoxy resin sealing material is shaped into a tablet shape, then put into a pot in the mold, heated and melted, pressurized with a plunger, transferred to the mold cavity, and cured. Is. However, in this molding method, the resin viscosity increases with time in the runner part or pot, which is a flow path until the sealing material charged in the pot flows in the mold and reaches the cavity, and the resin injection speed further increases. It can be considered as a cause of wire deformation due to the influence of.

  The technique described in Patent Document 1 is known as a prior art for the wire deformation described above. In Patent Document 1, a manufacturing method of a semiconductor manufacturing apparatus is disclosed in which a heating cylinder of an injection molding machine is divided into a plurality of zones in an injection molding machine, and each zone is independently temperature controlled.

  FIG. 3 is a diagram showing a temperature profile in a conventional method of manufacturing a semiconductor device, which is a time chart when performing transfer molding, in which the vertical axis indicates the mold temperature and the horizontal axis indicates the molding time.

  In the conventional method for manufacturing a semiconductor device, as shown in Patent Document 1 described above, as an epoxy resin sealing material, an epoxy resin, a curing agent, a curing accelerator, and an inorganic filler are included as essential components, The epoxy resin is a specific epoxy resin, and the epoxy resin sealing material whose curing agent is a specific phenol resin is used. The heating cylinder of the injection molding machine is divided into multiple zones, and the temperature of each zone is controlled independently. The most nozzle side zone is controlled to 65 to 110 ° C., and the most hopper side zone is controlled to room temperature to 50 ° C.

  In such a transfer mold, as shown in FIG. 3, the molding time of 30 seconds shown on the horizontal axis is a holding time for resin injection and curing. The mold temperature during this molding time is constant at 175 ° C. That is, in the conventional case, the conventional mold temperature is kept constant and the process from the injection of epoxy resin to the curing is completed.

  FIG. 4 is a diagram showing a speed profile in a conventional method for manufacturing a semiconductor device, which is a time chart when performing transfer molding, in which the vertical axis indicates the injection speed and the horizontal axis indicates the molding time.

  When the injection is performed in a state where the melt viscosity is low due to a decrease in the mold temperature at the time of injection, the resin quickly flows in the cavity, so that it becomes close to a turbulent state, so that voids due to air entrainment are likely to occur.

  For example, Patent Document 2 or 3 discloses a method of maintaining the mold temperature at the melting temperature of the sealing resin and increasing the mold temperature to the curing temperature of the sealing resin after the filling of the sealing resin is completed. Has been.

JP 2001-196402 A JP 2000-091367 A JP 2001-055432 A

  However, in the prior art shown in Patent Document 1, it is necessary to divide the heating cylinder of the injection molding machine into a plurality of zones, and to control the temperature of each zone independently, and the structure of the injection molding machine becomes complicated. In addition, there is a problem that the control is complicated at a high cost.

  In the prior art shown in Patent Document 2, the improvement factor of voids and wire flow refers only to the melt viscosity of the resin, and the resin injection rate is increased until just before the cavity gate in consideration of the curing characteristics of the resin. By setting a high speed, the time is shortened. Further, when the flow of the resin reaches the cavity region, the injection speed is suppressed in the region where the melt viscosity of the resin is low to prevent the air from being caught. Also, when the resin flow reaches the cavity region, in the region where the resin melt viscosity is high, the resin injection speed is increased within the range where the wire flow does not occur to shorten the time before the resin melt viscosity rises. There was a problem that the method for controlling the injection rate of the resin for completing the filling was insufficient.

  Furthermore, the prior art disclosed in Patent Document 3 is a reference to only the melt viscosity only by controlling the mold temperature as in Patent Document 2, and there is a problem that the method for controlling the injection rate of the resin is not considered. It was.

  The present invention has been made in view of such problems, and the object of the present invention is to provide an epoxy resin encapsulant in order to prevent voids and wire deformation by a simple method using a normal transfer molding machine. It is an object of the present invention to provide a semiconductor device in which a semiconductor element is resin-sealed by transfer molding using a stopper material and a method for manufacturing the same.

  The present invention has been made to achieve such an object. The invention according to claim 1 is directed to fixing a lead frame or a lead wire to which a semiconductor element is bonded to a transfer molding die, and performing the transfer molding. In a method of manufacturing a semiconductor device in which the semiconductor element is resin-sealed by press-filling and curing an epoxy resin sealing material on the mold with a transfer molding machine, when the semiconductor element is transfer-molded with the epoxy resin First, the epoxy resin is injected at a first mold temperature and a first molding time, and then at a second mold temperature and a second molding time higher than the first mold temperature. The epoxy resin is cured, and the injection rate of the epoxy resin has a plurality of different injection rates during the first molding time.

  The invention according to claim 2 is the invention according to claim 1, wherein the epoxy resin sealing material contains an epoxy resin, a curing agent, a curing accelerator, and an inorganic filler as essential components. It is characterized by that.

  The invention according to claim 3 is the invention according to claim 1 or 2, wherein the second mold temperature is 10 to 30 ° C. higher than the first mold temperature. .

  The invention according to claim 4 is the invention according to claim 1, 2 or 3, wherein the first mold temperature is 150 ° C. and the first molding time is 20 seconds. And

  The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the second mold temperature is 175 ° C. and the second molding time is 10 seconds. Features.

  According to the present invention, the epoxy resin is injected until the resin sealing material flows in the mold and reaches the cavity by ensuring a long time for injecting the low viscosity epoxy resin at the first mold temperature. It is possible to keep the viscosity of the resin low, and it is also possible to flow the epoxy resin into the cavity at a low speed, which can reduce the viscosity and the resin flow speed affecting the wire deformation for a long time. I can do it.

  Further, since the viscosity of the resin can be kept low, poor filling can be reduced. From this, wire deformation can be reduced because the resistance to the wire by the epoxy resin is reduced.

  Furthermore, by setting the second mold temperature higher than the first mold temperature, it is possible to accelerate the curing after filling the cavity in the mold with the epoxy resin and prevent the productivity from being lowered. At the same time, when the resin is injected in a state where the melt viscosity is low (refer to FIG. 4) due to a decrease in the mold temperature during injection, the resin quickly flows in the cavity, so that it becomes close to a turbulent state. It tends to occur. Therefore, the second injection speed (see FIG. 2) is switched to lower the resin injection speed in the cavity.

It is a figure which shows the temperature profile in the manufacturing method of the semiconductor device which concerns on this invention. It is a figure which shows the speed profile in the manufacturing method of the semiconductor device which concerns on this invention. It is a figure which shows the temperature profile in the manufacturing method of the conventional semiconductor device. It is a figure which shows the speed profile in the manufacturing method of the conventional semiconductor device.

Embodiments of the present invention will be described below with reference to the drawings.
In the method of manufacturing a semiconductor device according to the present invention, a lead frame or a lead wire to which a semiconductor element is bonded is fixed to a transfer molding die, and an epoxy resin sealing material is pressure-filled into the transfer molding die by a transfer molding machine. Then, the semiconductor element is resin-sealed by curing. When a semiconductor element is transfer-molded with an epoxy resin, first, an epoxy resin is injected at a first mold temperature and a first molding time, and then a second mold temperature higher than the first mold temperature. The epoxy resin is cured in the second molding time, and the injection rate of the epoxy resin has a plurality of different injection rates in the first molding time.

  The epoxy resin sealing material contains an epoxy resin, a curing agent, a curing accelerator, and an inorganic filler as essential components. Further, the second mold temperature is set 10 to 30 ° C. higher than the first mold temperature.

  As the epoxy resin sealing material, a material containing 80% or more of silica, 3% or more of epoxy resin, and 2% or more of a curing agent as a main component, and a mold release agent, a pigment, or the like was also used. Asahi Engineering Cosmo-T2 (plunger pressurization type) was used as the transfer molding machine, the first mold temperature was set to 150 ° C., and the second mold temperature was set to 175 ° C. The mold temperature is raised by controlling the current input to the heater set inside the mold. Further, the transfer pressure is set to 30 tons, the first mold temperature is set to 150 ° C. and the first molding time is held for 20 seconds, and then the second pressure set in advance is set. After the mold temperature is automatically raised to 175 ° C. and the second molding time is maintained for 10 seconds, the mold is opened and the molded product is discharged. The time from mold clamping to mold opening was 50 seconds, and the total molding cycle was 70 seconds.

  The die was joined to the IC element and the Hall element as a four-frame mold, and four 1,212 lead frames bonded with the gold wire were automatically set in the mold and continuously molded. The appearance, fillability, and wire sweep of the molded product (resin-sealed semiconductor) sealed every hour were measured.

  Table 1 shows the measurement results of appearance, fillability, wire sweep, and void every 5 hours.

The measurement method is as follows.
Appearance, fillability, void: Observation by visual observation, appearance was particularly good for gloss.
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 2 mm) was measured. The ratio of the maximum wire flow rate to the bonding diameter size (25 μm) was expressed in%.

  These results are shown to be superior to conventional sealing at a fixed mold temperature, and it has been confirmed that there is no problem at all. Therefore, it turns out that continuous molding is possible over a long time.

  FIG. 1 is a diagram showing a temperature profile in a method of manufacturing a semiconductor device according to the present invention, which is a time chart when performing transfer molding, in which a vertical axis indicates a mold temperature and a horizontal axis indicates a molding time.

  Specifically, the semiconductor device was manufactured as follows according to the mold temperature in the time chart of FIG. The used epoxy resin sealing material contains an epoxy resin, a curing agent, a curing accelerator and an inorganic filler as essential components, the epoxy resin is a specific epoxy resin, and the curing agent is a specific phenol resin. A sealing material was used. The transfer molding machine is a plunger pressurization type. In the case of the present invention, before injecting the epoxy resin, the mold temperature is kept constant at 150 ° C., and the sealing material flows in the mold and completely enters the cavity. After filling the mold, the mold temperature is further raised by 25 ° C., the temperature is kept constant for curing, and finally, the molded product is released from the mold, and the molded product is taken out from the mold. Is.

  According to the present invention, when the element molded by the method of the present invention and the element molded by the conventional method are compared by X-ray analysis, the wire sweep occurrence rate (that is, the gold wire diameter) equal to or larger than the gold wire diameter. On the other hand, when the maximum wire flow rate exceeds the gold wire diameter), the element molded by the method of the present invention is 0 ppm, but the element molded by the conventional method is generated at 5,000 ppm or more. In addition, voids of 200 μm or more are generated.

  FIG. 2 is a diagram showing a speed profile in the method for manufacturing a semiconductor device according to the present invention, which is a time chart when performing transfer molding, in which the vertical axis indicates the injection speed and the horizontal axis indicates the molding time.

  When the injection is performed in a state where the melt viscosity is low due to the lowering of the mold temperature (see FIG. 4), the resin quickly flows through the cavity, so that it becomes close to a turbulent state, and therefore voids due to air entrainment are likely to occur. . Therefore, the second injection speed is switched to lower the resin injection speed in the cavity.

Claims (5)

A lead frame or a lead wire to which a semiconductor element is bonded is fixed to a transfer mold, and the transfer mold is filled with an epoxy resin sealing material by a transfer molding machine and cured to thereby cure the semiconductor element. In the manufacturing method of the semiconductor device for resin sealing,
When the semiconductor element is transfer-molded with the epoxy resin, first, the epoxy resin is injected at a first mold temperature and a first molding time, and then a second temperature higher than the first mold temperature. The epoxy resin is cured at a mold temperature and a second molding time, and the epoxy resin injection speed has a plurality of different injection speeds during the first molding time. Device manufacturing method.   2. The method of manufacturing a semiconductor device according to claim 1, wherein the epoxy resin sealing material contains an epoxy resin, a curing agent, a curing accelerator, and an inorganic filler as essential components.   3. The method of manufacturing a semiconductor device according to claim 1, wherein the second mold temperature is 10 to 30 ° C. higher than the first mold temperature. 4.   4. The method of manufacturing a semiconductor device according to claim 1, wherein the first mold temperature is 150 ° C. and the first molding time is 20 seconds. 5.   5. The method of manufacturing a semiconductor device according to claim 1, wherein the second mold temperature is 175 ° C. and the second molding time is 10 seconds.

Images