JP4825572B2 - Resin sealing device and resin sealing method by transfer molding - Google Patents

Description

  The present invention relates to a resin sealing device and a resin sealing method by transfer molding.

  In the field of mounting electronic parts such as semiconductors, a bare chip whose circuit is designed by patterning technology such as exposure is cut out from the wafer, mounted on a die, and further connected to an external terminal by wire bonding or the like, and then sealed with resin. There is a process to stop. When this resin sealing is performed, a sealing method called transfer molding has been conventionally employed. This is a method of pouring (pushing) molten thermosetting resin (epoxy, etc.) through a runner and nozzle into a cavity in which a member to be sealed (substrate to be sealed) is mounted. There is an advantage that the member to be sealed can be sealed.

  In this method, a so-called thermosetting resin that accelerates curing by applying heat is used. However, after the molding is completed by pressing the resin, several minutes are spent for curing time for curing, and productivity is increased. There was a problem of low (long cycle time).

  More specifically, in transfer molding, a material in which a glass filler is mixed with epoxy is generally used, but in view of the curing speed of the material, the mold temperature is generally set to about 180 ° C. It is. The package thickness of the leading-edge semiconductor sealing is on the order of about 1 mm, and the mold temperature is set to flow through the entire cavity space where the molten resin is to be sealed before the sealing resin is completely cured. It is necessary to keep it below a certain level and raise it to the curing temperature after it has been drained.

  In the case of transfer molding, since the sealing cavity space varies depending on the batch, it is necessary to adjust the volume of the poured resin. The buffer portion that performs the volume adjustment is called a cull portion, and is coupled to a plurality of sealing cavities via a runner. In order to secure a certain buffer volume, the cull portion has a thickness several times that of other substrate mounting portions. For this reason, curing is the slowest and is rate-limiting in the process from mold opening to resin removal.

Japanese Patent Application Laid-Open No. H10-260260 discloses a device in which heating means such as a heater is provided in a mold.
Further, in Patent Document 2, as shown in FIG. 3, in addition to a normal heater 10, a resin encapsulating structure in which heat-absorbing and heating elements 16 and 17 are provided in the vicinity of a cull portion 12 and a cavity 14 of a mold. Stop devices have been proposed. The heat absorption and heating bodies 16 and 17 are surrounded by the heat insulators 18 and 19.

  At the time of extruding the resin seal, the calorie portion 12 and the cavity 14 are maintained at the melting temperature of the sealing resin by the endothermic action of the heat-absorbing heat generators 16 and 17, so that the viscosity of the sealing resin is appropriate. Thus, the extrusion speed of the resin in the cavity 14 can be maintained at an appropriate value. On the other hand, when the extrusion process is completed, the inside of the cull part 12 and the cavity 14 is heated to the curing temperature of the sealing resin by the heat radiation action of the heat-absorbing and heat generating bodies 16 and 17, and the curing of the resin is accelerated. .

JP 2002-299356 A JP 2000-91367 A

  However, since the difference in thermal conductivity between the resin (sealing material) and the steel material (mold) is about 100 times, as in the technique described in Patent Document 1, a heater or the like is simply placed in the mold. In the method of arranging the heating means, most of the heat supplied by the heater escapes from the mold having high thermal conductivity to the outside, and the heat from the heater is hardly transmitted to the resin to be heated. was there.

  In addition, in order to solve this problem, if the heat capacity of the heater is simply increased, not only will the running cost increase, but the heat received by the resin near the heater will become too large, such as the cull part, runner, cavity, etc. There is a tendency that a temperature distribution is likely to occur in each part of the substrate, particularly each part of the substrate surface, and there is a high risk of problems such as “warping” of the substrate.

  Further, as in the technique described in Patent Document 2, in the technique in which the heat absorbing and heating elements 16 and 17 are provided in the vicinity of the cull portion 12 and the cavity 14, the “heat absorbing and heating element” in which the accumulated heat is released. Because of this function, it is difficult to actively control heating, and good heating characteristics are not always obtained. Further, since it is necessary to incorporate heat-absorbing and heat generating bodies 16 and 17 having different thermal expansion coefficients into the “mold surface” in pairs with the heat insulating materials 18 and 19, there is a problem that it is actually difficult to manufacture. It was. Furthermore, the presence of the heat insulating materials 18 and 19 surrounding the heat absorbing and generating bodies 16 and 17 eliminates the escape of heat accumulated in the heat absorbing and generating bodies 16 and 17, so that it is difficult to control the cooling and the heat absorbing and generating elements 16 , 17 also had a problem that heat was sometimes accumulated too much. Since the temperature of the cull part 12, the runner 12, and the cavity part 14 of the mold needs to be lowered to a certain level or lower at the time of the next sealing, this problem is caused when the material to be sealed is changed. There was a big problem.

  The present invention has been made in consideration of the circumstances of such a conventional sealing environment, and is easy to manufacture and does not increase the overall cost of the apparatus, has high heat input efficiency, and reduces cycle time. An object of the present invention is to provide a resin sealing device that can be used and that is less prone to problems such as warping of the product.

The present invention provides a resin sealing device that seals a sealing member incorporating a semiconductor or the like by transfer molding in upper and lower molds, wherein the upper mold of the mold includes a cull portion and a cavity. a first upper die comprising, a second upper die to be overlaid thereon, first, the heat insulating layer is interposed between the second upper die, between the cull part and said heat insulating layer A heating source is disposed on an axis of the advancement / retraction of a plunger that is movably arranged in a pod formed in the lower mold of the mold, and includes the cull portion from the heating source. The above-described problems are solved by direct heat conduction to the first upper mold portion adjacent to the heating source.

  In the present invention, the upper mold is divided into a first upper mold that includes a cull portion and a cavity by dividing the upper mold vertically, and a second upper mold that is superimposed on the first upper mold, and then the first and second upper molds. A heat insulating layer is interposed between the two. Therefore, the mold has a simple shape and can be manufactured at low cost.

  In addition, since the entire first upper mold can be heated by the heat generated by the heating source, each part such as the cull part, the runner, and the cavity, particularly each part on the substrate surface, is locally heated. It is possible to minimize the occurrence of temperature distribution in the product, and it is possible to effectively prevent problems such as “warping” in the product.

  In addition, since the heating source is arranged between the cull part and the heat insulating layer, heating is performed around the cull part that requires the most heating capacity, and only in the first upper mold due to the presence of the heat insulating layer. Heat is transmitted. Therefore, the amount of heat escaping to the outside through the mold can be kept small, the heat input efficiency is high, and the heating source does not require a large capacity.

  Furthermore, since it is different from the method of locally insulating the heat generated locally, it is possible to effectively prevent a situation in which heat is excessively accumulated in the local portion. Therefore, it is possible to satisfactorily control both heating and cooling without providing a cooling means or the like (just by disposing a heating source).

  According to the present invention, the thermal efficiency is high, the manufacture is easy and the cost is low, the heat input efficiency is high, the cycle time can be reduced, and the occurrence of defects such as warping of the product can be prevented.

  In FIG. 1, the outline of the resin sealing apparatus which concerns on an example of embodiment of this invention is shown. FIG. 1 schematically shows the outline of the resin sealing device focusing on its function, and does not necessarily match the specific configuration of the actual device.

  The mold 24 of the resin sealing device 22 includes an upper mold 26 and a lower mold 28. The upper die 26 is further divided into upper and lower parts, and is mainly composed of a first upper die 30 and a second upper die 32 that is overlaid thereon. A heat insulating layer 34 is interposed between the first upper mold 30 and the second upper mold 32 to divide the first and second upper molds 30 and 32 horizontally. In this embodiment, the heat insulating layer 34 is made of a ceramic material having a strength capable of withstanding the clamping load of the mold 24.

  The first upper mold 30 corresponds to the upper side of the substrate K among the cull portion 36, the first and second recesses 38 and 40 where the substrate to be sealed is disposed, and the cavity 42 filled with the sealing resin. An upper cavity 44 is provided, and a local heater (heating source) 46 is provided above the cull portion 36. The local heater 46 is housed in a corrosion-resistant steel casing 47. The steel casing 47 has the same strength and thermal expansion coefficient as the first upper mold 30, and constitutes a part of the mold surface of the first upper mold 30.

  More specifically, in this embodiment, the dimension A1 from the upper surface 36A of the cull portion 36 to the lower surface 34A of the heat insulating layer 34 is set to about 0.7 times the thickness A2 of the cull portion 36. Constantly, the dimension A1 is set to be several times as large as 0 times the dimension A2 (that is, the local heater 46 is embedded in the cull part 36 and the upper part of the local heater 46 is in contact with the lower surface 34A of the heat insulating layer 34). Is preferred. In addition, as a dimension A3 between the cavity 42 and the heat insulation layer 34, it is preferable to secure about 1 to several times the thickness A4 of the cavity 42. If any of these dimensions is smaller than the respective lower limit, the input heat efficiency is increased. However, it is not preferable because the temperature distribution in the vicinity of the local heater 46 of the cavity 42 and the portion away from the local heater 46 tends to occur. . On the contrary, if it becomes larger than each upper limit, the capacity | capacitance of the 1st upper mold | type 30 will become large, and the advantage of this invention will be lost.

  In FIG. 1, the second upper mold 32 has a vertical thickness that is substantially the same as that of the first upper mold 30, but actually occupies most of the upper mold 26 and is not shown. It is attached to the stationary platen via an attachment block or the like.

  On the other hand, the lower die 28 is also attached to the movable platen via a known attachment block, a support plate, etc., although this is not shown. The movable platen is connected to a press device (not shown), and can be moved forward and backward (moved in the vertical direction in FIG. 1) by driving the press device. The lower mold 28 is brought into contact with and separated from the mold 30), and the mold 24 is closed, clamped and opened. However, in the present invention, either the upper mold or the lower mold may be a movable mold.

  In the lower mold 28, a runner 50 and a lower cavity 52 (corresponding to the lower side of the substrate K in the cavity 42) are recessed. Further, a cylindrical pot 54 is formed, and a plunger 56 is disposed in the pot 54 so as to be movable forward and backward.

  Although not particularly illustrated, the lower die 28 is embedded with a heater similar to a conventionally provided heater for mold heating.

  Next, the operation of the resin sealing device 22 will be described.

  With the plunger 56 placed at the lower limit position, a resin material (molding material) 58 such as a tablet or a pellet is set in the pot 54, and the rise of the plunger 56 causes the cull portion 36 and the runner 50 to move under the melting temperature. The resin material 58 flows into the upper and lower cavities 42 and 52 formed above and below the substrate K. Thereafter, the temperature is raised in a state where the mold is clamped by the upper mold 26 and the lower mold 28, the mold is opened when the resin is cured, and the resin-sealed substrate K is taken out. This series of basic sealing process itself is not particularly different from the conventional one.

  In the resin sealing device 22, a local heater 46 is installed adjacent to the cull portion 36 that is the most delayed portion of curing, and the upper die 26 includes a cull portion 36, a cavity 42, and the like. And a second upper mold 32 superimposed on the upper part, and a heat insulating layer 34 is horizontally disposed therebetween. In this configuration, since the most important part of the mold does not need to be greatly changed in design, there is almost no problem of an increase in cost for carrying out the invention.

  In addition, the heat supplied by the local heater 46 propagates only in the first upper mold 30 while transferring the largest amount of heat to the nearest cull portion 36. Therefore, even if the heat capacity of the local heater 46 is reduced, the cull portion 36 can be efficiently heated.

  In addition, since the generated heat spreads over almost the entire first upper mold 30, a temperature distribution that causes problems such as warpage around the substrate K hardly occurs.

  Furthermore, since the local heater 46 is not directly surrounded by the heat insulating material, heat can be appropriately dissipated from this portion via the first upper mold 30. Therefore, there is no problem that heat is accumulated only in this portion (no heat escape). That is, the first upper mold 30 also has a function of appropriately cooling the heat around the local heater 40. Therefore, even if the cooling mechanism is not provided separately, both heating and cooling can be controlled satisfactorily only by arranging the local heater 46. The mold in transfer molding needs to be cooled to a melting temperature, that is, a predetermined temperature or less when the resin material 58 is pushed in, so this cooling function is important in order to realize a smooth sealing cycle. is there.

  FIG. 2 shows an example of another embodiment of the present invention.

  In this embodiment, a space 170 for assembling the local heater 146 is secured in the first upper mold 130, and the local heater 146 is incorporated in the space 170 without being in contact with the resin material 158 of the cull portion 136. Yes. Therefore, the mold surface of the first upper mold 130 only needs to be designed in exactly the same way as before, and the resin material 158 can be introduced into the cavity 142 as in the original mold design.

  Further, in this embodiment, the local heater 149 is incorporated not only in the vicinity of the cull portion 136 but also in the vicinity of the cavity 142. Thus, in the present invention, it is not prohibited to arrange the local heater at a position other than the vicinity of the cull portion.

  About another structure, it is the same as that of previous embodiment, and the same effect is obtained. For this reason, the same or similar parts in the figure are given the same reference numerals in the last two digits as in the previous embodiment, and redundant description is omitted.

  In each of the above embodiments, the heat insulating layer is made of ceramic, but the configuration of the heat insulating layer according to the present invention is not limited to this. Since the heat insulating layer according to the present invention has a simple shape and is only subjected to compressive stress, various heat insulating layers can be employed. For example, it may be formed of resin at a lower cost, or may be formed of an air heat insulating layer having a honeycomb structure. Further, two or more heat insulating layers may be interposed.

  The present invention can be applied to an apparatus for resin-sealing a substrate such as a semiconductor by transfer molding.

The schematic block diagram which shows typically the principal part of the resin sealing apparatus which concerns on an example of embodiment of this invention. The schematic block diagram which shows typically the principal part of the resin sealing apparatus which concerns on an example of other embodiment of this invention. Schematic configuration diagram schematically showing the main part of a conventional resin sealing device

Explanation of symbols

DESCRIPTION OF SYMBOLS 22 ... Resin sealing device 24 ... Mold 26 ... Upper mold 28 ... Lower mold 30 ... 1st upper mold 32 ... 2nd upper mold 34 ... Heat insulation layer 36 ... Cull part 42 ... Cavity 44 ... Upper cavity 46 ... Local heater ( Heating source)
47 ... Casing 50 ... Runner 52 ... Lower cavity 54 ... Pot 56 ... Plunger 58 ... Resin material

Claims (4)

In a resin sealing device that seals a sealing member incorporating a semiconductor or the like by transfer molding in upper and lower molds,
The upper mold of the mold includes a first upper mold including a cull portion and a cavity, and a second upper mold superimposed on the upper mold.
A heat insulating layer is interposed between the first and second upper molds,
It is between the cull part and the heat insulating layer, heat source is disposed on the axis of該進retracted in the mold plunger forward and backward movably disposed within the pod which is formed in the lower mold of the And
A resin sealing device by transfer molding, wherein direct heat conduction is performed from the heating source to the portion of the first upper mold adjacent to the heating source including the cull portion.   The resin sealing device according to claim 1, wherein the heat insulating layer is made of a ceramic material. In claim 1,
A resin sealing device by transfer molding, wherein the heat insulating layer is composed of an air heat insulating layer having a honeycomb structure. In a resin sealing method for sealing a sealed member incorporating a semiconductor or the like by transfer molding in upper and lower molds,
An upper mold of the mold is formed by a first upper mold including a cull portion and a cavity and a second upper mold superimposed on the upper mold, and between the first upper mold and the second upper mold. A step of interposing a heat insulating layer;
Heating disposed on the axis of the forward / backward movement of the plunger disposed between the cull portion and the heat insulating layer and freely movable in the pod formed in the lower mold of the mold. And heating the entire first upper mold around the cull portion by a source. A resin sealing method by transfer molding, characterized by comprising:

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