JPH03256712A - Transfer molding machine - Google Patents

Abstract

PURPOSE:To obtain an apparatus with a simple structure an at a high yield of a resin and to obtain a molded item with uniform quality by providing a pot for feeding a molding material, a plunger with a same shape moving back and forth in the pot and a plurality of cavities and making a crosssectional shape wherein a distance between the pot and each cavity is roughly equal. CONSTITUTION:A pot 9 formed in a top force is made in a roughly rectangular shape and a plunger 10 is also made in a rectangular shape fitted to the shape so as to move it back and forth therein. Then, a lead frame 11 fixed with a chip is set in a cavity 3 and the pot 9 is placed in the center of the lead frame 11 in a parallel with the lead frame 11. In addition, a runner 12 is connected with a gate 4 of each cavity 3 vertically from the pot 9 at an approximately equal distance. In accordance with the shortened amt. of length of the runner, loss of a resin material is decreased and the yield is improved. In addition, it is possible to accomplish rapidly and efficiently feeding and molding and to obtain a molded item with high quality by keeping inflow pressure of the resin into the cavity at an ordinary state. The pot may have a cross-shaped crosssection and a L-shaped crosssection.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Field of Application) The present invention relates to a transfer molding apparatus, and in particular to a plunger and a pot of a transfer molding apparatus used for resin-sealing manufacturing of semiconductor devices. It's about structure.

(Prior Art) In the resin encapsulation method applied to semiconductor devices such as ICs and LSIs, the resin not only adheres to the surface of the semiconductor chip and completely covers it, but also has excellent heat resistance. Recently, it has been rapidly used because it has various characteristics such as not having a negative effect on chip characteristics and has low internal stress, and can be manufactured at low cost. As a method of resin sealing,
dipping method, casting method, botting method,
Although transfer molding methods, impregnation methods, and the like are known, the transfer molding method is currently widely used.

The transfer bottom profile is performed in a conventional manner. The semiconductor element assembly (lead frame with chip installed) to be sealed in a mold that has been heated to a certain temperature in advance is placed in the lower mold cavity, and the mold is closed.
The tablet-shaped resin is preheated with a high-frequency preheater to improve its flow inside the mold, and then placed in a pot and operated by the transfer plunger, which injects the resin into the cavity through the runner and gate, pressurizes it, and molds it. do. Press for 1 to 3 minutes until the resin is partially cured. The pressure in this case is about 20-100 kg/d.

The number of cavities varies from several dozen to approximately 1000, depending on the size of the cavities. When it has hardened and can be removed.

Open the mold and take out the molded product along with the cull runner.

Thereafter, resin particles adhering to the mold are removed using high-pressure air, etc., and then the lead frame is set in the mold again and the same operation is repeated. The molded product taken out of the mold is separated from the cull runner, after-cured, deburred, plated, and cut, then tested and marked.

Conventionally, there are two types of devices for carrying out this transfer molding method: a one-pot plunger system and a multi-pot plunger system. The former uses one cylindrical plunger and the same pot, and the resin from the pot is supplied to multiple cavities through multiple runners, while the latter uses multiple pairs of pots and plungers. Each pair joins one or two cavities.

The conventional one-pot plunger system transfer molding device has a plurality of pairs on the contact surfaces of the upper mold 1 and the lower mold 2 of the six devices shown in FIGS. The cavities 3 are arranged facing each other, and an auxiliary runner 6 is formed in the opposed middle part to communicate with the cavities 3 through a gate 4, and a main runner 8 is formed branching from a cull part 7 formed in the center of the center block. Using a transfer molding die communicating with the auxiliary runner 6, a lead frame with a semiconductor chip attached thereto is set on the contact surface between the upper mold 1 and the lower mold 2, and the molds are clamped. Next, a tablet-shaped thermosetting synthetic resin such as preheated epoxy resin or silicone resin is supplied into a cylindrical pot 9 provided in the center of the upper mold side, and this molding material is passed through a cylindrical plunger. Pressurize at 10. The molding material plasticized in the pot 9 by this pressurization is injected under pressure into the cavity 3 via the main runner 8, the auxiliary runner 6, and the gate 4, and is molded with the semiconductor chip encapsulated therein. However, when molding is performed using this equipment, the resin has a long flow distance from the pot to each cavity, so the hardening of the resin is accelerated over time during the flow process, and the quality of the molded product is affected by differences in the positions of the cavities. If the injection pressure of the resin is increased to increase the flow speed to eliminate this defect, the inflow pressure into the cavity becomes too strong and the inner leads of the chip and lead frame are damaged. Thin metal wires called bonding wires may be washed away, the adhesion between the lead frame and the chip may deteriorate, and air may not be removed sufficiently, causing cavities to form inside and outside the molded product. Another major drawback is that the resin used also fills the cull, part of the runner, and the gate and solidifies in those areas, so much of the resin is not used in the product.
The yield of the resin used will be significantly lower. At best, this yield is about 60%, and at worst, it may fall below 20%. Furthermore, the flow distance may vary from cavity to cavity, causing variations in the quality of molded products.

Further, FIG. 3 shows a plan view of a multi-pot system transfer molding apparatus including a pot, a cavity, and a runner gate.

In this device, a plurality of pairs of cavities 3 are arranged facing each other, a pot 9 for each pair is arranged in the center of each pair, and the pot 9 is connected to the cavity 3 via a runner 12 and a gate 4. That is, it is characterized by the use of a plurality of pots and plungers. With such a configuration, it is possible to shorten the resin flow distance, reduce resin loss, and improve yield at the same time. Moreover, molded products with good quality and no variation can be obtained. However, since there are a large number of plungers in one device, the structure becomes complicated, and, for example, the pot often wears out due to the inorganic filler in the resin, which makes maintenance difficult.

Placing a large number of small tablets on a preheater, transporting a large number of tablets at once, and placing them in each pot are difficult tasks, and the more plungers there are, the greater the probability of failure or incorrect adjustment. becomes larger.

(Problems to be Solved by the Invention) Conventional transfer molding apparatuses have many problems that need to be solved in both one-pot plunger systems and multi-pot plunger systems. The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a transfer molding apparatus with a simple structure that can produce molded products with good resin yield and uniform quality.

[Structure of the invention]

(Means for Solving Problem W) The present invention provides a resin molding mold in which an upper mold and a lower mold are arranged facing each other, one molding material supply pot disposed in this mold, and this pot. The present invention relates to a transfer molding device comprising a plunger having the same shape and reciprocating within the pot, and a plurality of cavities communicating with the plunger via a runner and a gate, the pot comprising: It is characterized by having a cross-sectional shape such that the distances from the pot to each cavity are approximately the same.

(Function) By employing the above configuration, the structure of a part of the plunger is simplified and the flow distance of the resin is shortened.

(Example) An example of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1(a) is a perspective view of the plunger, FIG. 1(b) is a perspective view of the pot, and FIG. 2(a) is a schematic plan view of the portion consisting of the pot, cavity gate, and runner. be. The pot 9 formed in the upper mold has a substantially rectangular shape, and the plunger 10 is also rectangular to match the shape so that it can reciprocate within the pot 9. FIG. 2(a) corresponds to this pot 9. In this figure, a lead frame 11 with a chip attached is set in a cavity 3. The pot 9 is arranged in parallel to the lead frame 11 at the center of the pair of lead frames 11. Cavities 3 are located in this l pair of lead frames, and runners 12 extend vertically from pot 9 and connect to gate 4 of each cavity 3. That is, the distances between the pot 9 and each cavity 3 are approximately equal.

When resin is supplied to this pot 9 and a rectangular plunger applies pressure to the pot, the resin is filled into the cavity 3 through the runner and the gate, and each chip on the lead frame is sealed with the resin.

The length of the runner can be shorter than that of conventional one-pot plunger systems, reducing the amount of resin material that is filled into the runner and helping to improve yields. This is particularly noticeable when a thermosetting resin is used as the encapsulating molding material. In addition, since the flow distance of the molding material is short, encapsulation molding can be performed quickly and efficiently, and there is no acceleration of hardening of the thermosetting resin over time, so there is no need to increase the flow rate of the resin. , the inflow pressure of resin into the cavity can be maintained at a normal state, and damage to semiconductor device parts such as bonding wires caused by excessive inflow pressure, internal and external voids caused by air, and resin and leads can be prevented. It is possible to obtain a high-quality molded product without deterioration of adhesion with the frame or chip.

In this example, a pot with a rectangular cross section as shown in Fig. 2(a) was chosen so that the distances from the pot to each cavity were all approximately equal, but the shape is not particularly limited. For example, it may be cross-shaped in cross section as shown in Fig. 2(b), or it may be
The cross-section may have a truncated shape as shown in Figure (c). In any case, if you arrange the cavities as shown in each figure, the distance to each cavity will be the same for all pot shapes. Molding molds using these pots can effectively utilize the inside of the molding apparatus, and are therefore useful for downsizing the apparatus.

In FIGS. 2(b) and 2(c), the description of the lead frame and the cavity is simplified, but the cavity is naturally installed at an arbitrary position depending on the shape of the pot via the runner and the gate. Moreover, since a pot of any shape can be used depending on the shape of the transfer molded snow covering, it is useful for effective use of the molding apparatus.

〔Effect of the invention〕

Since the present invention uses the plunger and pot configured as described above, it is possible to pressurize the molding material in the pot evenly, and a uniform molded product can be efficiently molded.
In addition, the reliability of this type of molded product, which requires high quality, is significantly improved.

In addition, the yield of resin is improved, and maintenance of a part of the plunger becomes unnecessary.

[Brief explanation of drawings]

Figure 1 (a), (b) and Figure 2 (a), (
b), (c). Each part of a transfer molding apparatus according to an embodiment of the present invention is shown, and FIG. 1(a) is a perspective view of a plunger, and FIG.
b) is a perspective view of the pot, FIG. figure(
c) is a schematic plan view of another example of the above part, FIG. 3 is a plan view of a conventional multi-pot plunger system, and FIG. 4(a) is a cross-section of a transfer molding device of a conventional one-pot plunger system. The figure and the same figure (b) are the top views. 1... Upper mold, 2... Lower mold, 3...
・Cavity, 4...Gate, 6...Auxiliary runner, 7...Cull part, 8...Main runner, 9...Pot. 10... Plunger 11... Lead frame. 12...Runner (8733) Agent Patent Attorney Inomata Yoshiaki (and 1 other person) Mouth (a,) Kaya 1 Ko (b) Matsuri 2 Sen Cb) Houki Sounen

Claims (1)

[Claims] A resin molding mold in which an upper mold and a lower mold are arranged facing each other, one molding material supply pot disposed in this mold, and having the same shape as this pot and reciprocating inside this pot. In a transfer molding device comprising a plunger and a plurality of cavities communicating with the plunger via a runner and a gate, the pot has a cross section such that distances from the pot to each cavity are approximately the same. A transfer molding device characterized by having a shape.