Conventional resin molding semiconductor devices have been manufactured by mounting semiconductor elements on a substrate, connecting electrodes on each semiconductor element to electrodes on the substrate via bonding wires, and molding the integrated semiconductor device with resin so as to wrap the semiconductor device. Specifically, the conventional resin molding semiconductor device has been manufactured by executing a resin molding process (transfer mold) comprising installing the semiconductor device in a cavity of a mold, injecting and filling a molten resin into the cavity through a gate, and hardening the resin.
As the advanced information-oriented society develops, stronger demands have been made to reduce the sizes and thicknesses of a group of products in the small electronic equipment field which are used in the advanced information-oriented society, and improve the functions thereof. In connection with the manufacture of semiconductor elements, key devices for the group of products, a reduction in the sizes and pitches of semiconductor elements has been strongly demanded. Resin molding semiconductor devices with the semiconductor elements mounted thereon are strongly demanded to have a structure including long wires or narrow pat pitch connections and in which electrodes on the semiconductor elements are electrically connected to many electrodes mounted on the substrate.
A method for manufacturing the resin molding semiconductor device has included the step of injecting resin into the cavity of the mold through the side surface of the cavity. However, with this method, the resin flows along the direction in which wires are arranged. Consequently, a wire coming into contact with the resin may be swept away by the resin to flow toward the adjacent wire. In this case, the wires contact each other to cause a short circuit.
A manufacturing method for inhibiting such a problem is proposed by, for example, Japanese Patent Laid-Open No. 2005-347514. According to this method, a gate is formed on a surface of the cavity which is located opposite a front surface of the semiconductor element and the resin is ejected from the gate toward the front surface of the semiconductor element.
With reference to FIGS. 28A to 28C and 29, a description will be given of a method for manufacturing such a conventional resin molding semiconductor device as described above. FIG. 28A is a plan view of a resin molding semiconductor device having a gate, that is, a resin injection port, formed on a surface of a cavity which is located opposite a front surface of each semiconductor element. FIG. 28B is a sectional view of the resin molding semiconductor device taken along line A-A′ in FIG. 28A. FIG. 28C is an enlarged plan view of a portion B in FIG. 28A. FIG. 29 is a sectional view showing a production equipment for manufacturing the resin molding semiconductor device.
As shown in FIGS. 28A to 28C and 29, the resin molding semiconductor device is manufactured by mounting a semiconductor element 52 on a substrate 51 and injecting a molding resin 54 toward a front surface of the semiconductor element 52 through a gate (resin injection port) 53 formed on a surface of a cavity 64 in molds 61, 62, and 63 which is located opposite the semiconductor element 52, to fill the cavity 64 with the molding resin 54. Here, reference numeral 55 in FIG. 28B denotes a wire, and reference numeral 56 denotes a solder ball. In FIG. 29, reference numerals 61, 62, and 63 denote an upper mold, an intermediate mold, and a lower mold, in order. Reference numeral 65 denotes a plunger for pushing the molding resin 54 into the cavity 64 through a runner 66. Reference numeral 67 denotes an air vent portion formed in an area of the upper mold 61 which is located opposite a top surface of the substrate 51.
In connection with such a resin molding semiconductor device, for example, Japanese Patent Laid-Open No. 2000-124239 proposes the production of a resin molding semiconductor device involving executing one molding process to mold a plurality of semiconductor elements 52 in order to reduce production time and subsequently cutting the semiconductor elements 52 off from one another.
However, even with the manufacturing method of forming the gate (resin injection port) in the surface of the mold located opposite the surface of the semiconductor element and ejecting resin from the gate to the surface of the semiconductor element, the following problem may occur. When the conventional method for manufacturing a resin molding semiconductor device wherein air in the cavity is discharged from the side surface of the cavity in the mold located along the surface of the substrate, is adopted, a plurality of semiconductor elements are mounted on one substrate and molded at a time to manufacture a large number of resin molding semiconductor devices at a time, the cavity area on the substrate increases consistently with the number of resin molding semiconductor devices. This significantly increases the distance from the resin injection port to the air vent for air discharge into which the resin is finally injected. As a result, during rein injection, air is likely to be mixed in the resin molding portion, where an internal void is thus likely to occur.
In the resin molding semiconductor device, when such a void is present in the resin, the resin is likely to be cracked at the void. This affects the reliability of the resin molding semiconductor device.
This also limits the size of the cavity, preventing an increase in the area that can be molded at a time. As a result, productivity cannot be improved.