JPS6122467B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a package forming method for airtightly housing semiconductor elements such as diodes and transistors, and integrated circuits of these semiconductors (hereinafter referred to as semiconductors). At least one of the pieces is sandwiched between two thermoplastic resin plate-shaped molded products (hereinafter referred to as thermoplastic resin plate-shaped bodies) each having a recess whose peripheral side wall portion has a thickness that varies depending on the position for storing semiconductors. The present invention relates to a method for manufacturing a thermoplastic resin flat package and dual in-line package, which are characterized by being integrally sealed. Traditionally, there have been two packaging methods for semiconductors: one that uses metal, ceramics, glass, etc. for airtight sealing, and the other that uses plastic. Recently, inexpensive plastic packaging has become popular due to improvements in reliability due to advances in chip protection technology. It has become mainstream. There are two types of plastic packages currently in practical use, the so-called molding method and the injection method, depending on the manufacturing method. Among them, epoxy resin transfer resin has excellent adhesion to metals, moisture resistance, electrical and mechanical properties, etc. Plastic packaging made by the Armold method is most commonly used. In this molding method, as shown in FIG. 1, a lead frame 5 in which electrodes of a semiconductor chip 2 on a tab 1 and leads 4 are electrically connected by thin metal wires 3 made of gold, aluminum, etc. is attached to an upper mold 6 and In this method, the cavity 8 is filled with molding resin material by a transfer molding machine, which is sandwiched between the lower molds 7 and through sprues, runners, and gates (not shown). The disadvantages of this method are variations in the thickness of the lead frame, precision of mold processing, and wear due to use.
Due to dimensional errors, etc., a gap is created between the mold and the lead frame, and flashes often appear in and around this area.These flashes on the leads are caused by poor contact between the lead and the socket, or due to soldering work. There were drawbacks such as the need for removal work as it caused obstruction. Furthermore, in this method, the chip is subjected to high temperature and high pressure conditions due to direct contact with the molding resin material during encapsulation molding with resin, which may affect the reliability of the semiconductor function in some cases. There were also drawbacks. In order to solve such drawbacks, at least one pre-formed material as shown in FIG. 2 and FIG.
2. The piece has a recess for storing semiconductors.
The thermoplastic resin plate-like bodies 10, 10' are attached to flat molds 9, 9' having a press function, and are necessary for combining with the lead frame 5 equipped with semiconductors (not shown in the figure) using a heater 12. A packaging method for semiconductors has been proposed in which the lead frame is heated to a certain temperature and molten resin is poured into the lead gap 13 of the lead frame using press pressure to fill the gap. However, this method also had the following drawbacks. In other words, the process of heating and melting the joining surfaces of the thermoplastic resin plates and then applying pressure with a press with the lead frame in between is a process in which the lead frame is placed on the joining surface of the heated and melted thermoplastic resin plates. This process consists of a process in which the leads are pushed in by press pressure () and a process in which the molten resin removed by the pushing of the leads flows into the lead gap and fills it. In the process (), the molten resin flows over the lead surface due to press pressure, pushing out the air existing at the boundary between the lead surface and the combined surface of the thermoplastic resin plate, and the lead surface is covered with resin. Wetting improves adhesive strength. In the process of (), the molten resin flows through the lead gap, eliminating the existing air and filling the lead frame with the lead frame. are combined. When the pressure necessary to obtain sufficient adhesion is applied, the amount of lead pushed in increases in the process of (), and the excess molten resin becomes a flash even after filling the gap between the leads in the process of (). This results in water flowing out around the outside of the combined part of the package and into the recesses inside. As with resin molds, flashes around the outside of the package assembly may cause poor contact between the leads and sockets and hinder soldering work. This poses a fatal problem in that it may destroy the metal thin wire joints provided. The present invention has been made in view of these points, and its contents will be explained below with reference to FIGS. 4 to 6 showing one embodiment. In FIG. 4, depressions 11, 11' having peripheral thin side walls 15, 15' and thick side walls 16, 16' for storing preformed semiconductors and the thick side walls formed when fused together. Two thermoplastic resin plates 17, 17' with molten resin reservoir depressions 18, 18' for collecting excess resin, and a semiconductor mounted thereon (not shown in the figure). The lead frame 5 is attached to the molds 14 and 14' with depressions, and the lead frame and the thermoplastic resin plate are heated to a predetermined temperature and then pressurized by a press to fuse the thermoplastic resin plate. . At this time, the recessed molds 14 and 14' to which the thermoplastic resin plate is attached are provided with recesses 19 and 19' for attaching the thermoplastic resin plate to which the thermoplastic resin plate can be closely attached. There is. The shape of the depression is such that the depth _t2 is the thickness of the thermoplastic resin plate.
The thermoplastic resin plate has the same shape as the thermoplastic resin plate at least around the opening of the recess except that it is smaller than t ₁ , and the outer surface of the thermoplastic resin plate is attached to the wall surface of the recess at least around the opening. The shape allows for close contact. The part corresponding to t ₁ - t ₂ is the resin part that melts and flows during fusion, and this amount is determined by the shape of the lead frame, but t ₁ - t ₂ is
No harmful flash was observed when the diameter was 0.1 mm or more and 0.7 mm or less, preferably 0.2 mm or more and 0.5 mm or less, and sufficient airtightness was obtained. When the thickness was less than 0.1 mm, the amount of resin that could melt and flow was small, and sufficient airtightness could not be obtained. In addition, if the distance exceeds 0.7 mm, the distance between the joining surface of the thermoplastic resin plate and the mold is too large, and as a result, the heat dissipation to the mold is delayed, and the temperature around the outside of the joining surface becomes higher than necessary, causing melting. The viscosity of the resin decreased and the occurrence of harmful flash was observed. The mold has a temperature controllable structure, and the temperature varies depending on the melt flow characteristics of the thermoplastic resin used as the material for the thermoplastic resin plate and the amount of molten resin, but it is kept at a temperature that does not cause harmful flashing. need to be kept. By using a mold with depressions for mounting and cooling such a thermoplastic resin plate, flashing to the outside of the package was suppressed, and as a result, the amount of flashing to the depressions 11 and 11' was reduced. However, in the present invention, at least one or more depressions 18, 18' are provided in the thick side wall to prevent the molten resin from causing flashing when heating and pressurizing the leads and the resin to an extent necessary and sufficient for adhesion. By pouring the lead into the recess, flashing to the recesses 11 and 11' storing semiconductors is minimized and damage to the connecting part of the thin metal wire provided at the tip of the lead is completely eliminated. was completed. Example 1 A thermoplastic resin body having a shape as shown in Fig. 5 was molded using polyphenylene sulfide (Ryton PPS: R-4, manufactured by Philips Corporation), and a 250μ thick 16mm body was mounted with a semiconductor integrated circuit. As shown in Figure 4, the pin DIP type lead frame was attached to a concave mold for pressurization and combination kept at 30°C, heated for 5 seconds with a 400°C heating platen in between, and then the heating platen was removed and pressure was applied. They were combined under pressure at 30 mg/cm ³ . After assembly, the flash inside and outside of the package was inspected, any breakage was confirmed using an IC tester, and the airtightness was confirmed using a red alcohol solution immersion test under pressure of 5 ft/cm ² in an autotale. As shown in Table 1, the results were all good. Example 2 Combining was carried out in the same manner as in Example 1, except that the temperature of the recessed mold was kept at 60°C. The obtained semiconductor package had good results as shown in Table 1. Example 3 Coalescence was carried out in the same manner as in Example 1, except that the heating method was heating with hot air at 450° C. for 10 seconds.
The obtained semiconductor package had good results as shown in Table 1. Example 4 The heating method was 30℃ using radiant heat from a heater at 800℃.
Coalescence was carried out in the same manner as in Example 1 except that the second heating method was used. The obtained semiconductor package had good results as shown in Table 1. Comparative Example 1 Combination was carried out in the same manner as in Example 1, except that the temperature of the mold for combination was kept at 100°C. The resulting semiconductor package had defects as shown in Table 1. Comparative Example 2 The thermoplastic resin plates were assembled in the same manner as in Example 1, except that the thermoplastic resin plates were not provided with the depressions 18 and 18' shown in FIG. The resulting semiconductor package had defects as shown in Table 1. Comparative Example 3 Combination was carried out in the same manner as in Example 1, except that a flat mold without the recesses 19 and 19' shown in FIG. 6 was used as the mold for combination. The resulting semiconductor package had defects as shown in Table 1. Comparative Example 4 The joining mold was a flat mold kept at 30°C, and the thermoplastic resin plate-like body had depressions 18 and 1 in Fig. 5.
Coalescence was carried out in the same manner as in Example 1, except that one without 8' was used and the coalescence pressure was 15 ft/cm ³ . The resulting semiconductor package had defects as shown in Table 1.

[Table] As explained above, the following effects are achieved in the present invention. 1. By using a thermoplastic resin plate, at least one of which has a recess for accommodating semiconductors, there will be no damage to the connections between the semiconductors and the leads, and the connections between the semiconductors, thin metal wires, and the tips of the leads will be eliminated. The reliability of the semiconductor function is improved because it is difficult for ionic impurities to come into contact with the resin because it is not in contact with the resin. 2 Compared to the conventional mold sealing method using thermoplastic resin, the resin viscosity is higher during fusion and coalescence, and by cooling the mold, only the outer periphery of the merging surface can be kept at an even higher viscosity. Since almost no flashing occurs, the process can be reduced.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing a method for forming packages for semiconductors using a molding method, Figures 2 and 3 are cross-sectional views showing a general method for forming packages using thermoplastic resin, and Figure 4 is a cross-sectional view showing a method for forming packages for semiconductors using a molding method. FIG. 5 is a plan view showing an example of the combined surface shape of the thermoplastic resin plate used in the present invention, and FIG. 6 is a cross-sectional view of the mold used in the present invention. It is a figure which showed an example and the connection with a thermoplastic resin plate-shaped body. Explanation of symbols, 1...Tab, 2...Semiconductor chip, 3...Metal thin wire, 4...Lead, 5...Lead frame, 6...Upper die, 7...Lower die, 8...
Cavity, 9,9'...Flat mold, 10,1
0'... Thermoplastic resin plate, 11, 11'... Hollow, 12... Heater, 13... Lead gap, 1
4,14'...Mold with recess, 15,15'...Thin side wall part, 16,16'...Thick side wall part, 17,1
7'... Thermoplastic resin plate-shaped body with depression for molten resin reservoir, 18, 18'... depression for molten resin reservoir, 1
9, 19'... Recess for mounting thermoplastic resin plate.

Claims (1)

[Scope of Claims] 1. A lead on which semiconductors are mounted, which is made of two thermoplastic resin plate-shaped molded products, at least one of which has a recess for accommodating the semiconductor, the peripheral side wall of which has a different thickness depending on the position. In a package molding method for semiconductors in which thermoplastic resin plate-shaped molded products are fused together by sandwiching a frame and heating and pressurizing, the thickness of the thin side wall portion of the thermoplastic resin plate-shaped molded product formed by the depression, excluding the merging surface. Either the joining surface of the thick side wall part, or, in the case of a thermoplastic resin plate-shaped molded product without a depression, the joining surface corresponding to the thick side wall part of the thermoplastic resin plate-shaped molded product that has a depression when fused and combined. Or a thermoplastic resin plate-shaped molded product having at least one depression for storing molten resin at at least one location on both sides, and a mold with a depression for fixing and cooling the thermoplastic resin plate-shaped molded product during fusion. A method for molding packages for semiconductors, characterized by using. 2. A method for molding a package of semiconductors according to claim 1, wherein the heating method is a method of contacting with a hot platen. 3. A method for molding a semiconductor package according to claim 1, wherein the heating method is hot air. 4. A method for molding a semiconductor package according to claim 1, wherein the heating method is radiation. 5. A method for molding a package for semiconductors according to any one of claims 1 to 4, wherein the temperature of the mold is adjusted to a temperature that does not cause flashing that is harmful to semiconductor packages. 6 The depression of the mold for attaching the thermoplastic resin plate-shaped molded product shall have a difference between its depth t ₂ and the thickness t ₁ of the thermoplastic resin plate-shaped molded product, t ₁ - _{t 2} of 0.1 mm or more and 0.7 mm or less. Any one of claims 1 to 5, wherein the depression has a shape that allows the wall surface of the depression and the outer surface of the thermoplastic resin plate-shaped molded product, excluding the combined surface, to be in close contact with each other at least around the opening of the depression. A method for forming packages for semiconductors as described in the above.