Method and apparatus for encapsulating semi-conductors

#The present invention relates to a resin-molded semiconductor and to an apparatus for producing the same. More particularly, it relates to a resin-molded semiconductor which can be produced with an improved use efficiency of resin and to an apparatus provided with a mold for the resin-molded semiconductor.

#Recently the multipot molding system has come into general use to rationalize the molding step for semiconductors. According to this system, one mold is provided with a plurality of pots and plungers and the molding resin is transferred into each cavity from each pot through a short runner. An advantage of this system over the conventional monopot molding system is that the molding resin can be used efficiently and the molding cycle can be reduced. On the other hand, this system compels one to use an extremely expensive molding resin incorporated with a large amount of high-purity filler in the case of semiconductors such as memory packages which require a high reliability. This makes it necessary to improve the use efficiency of resin to a great extent.

#An example of the conventional multipot molding apparatus is disclosed in Japanese Patent Publication No. 35576/1982. It is constructed such that one mold has a plurality of pots and the molding resin is fed under pressure to them through the runners which are independent from one another. However, it is still unsatisfactory in the use efficiency of molding resin. In other word, there is a limit in improving the ratio of the amount of resin in the cavity to the amount of total resin including resin in pots and runners. This is because the cavities are disposed in parallel with each runner and the flow path in the mold is limited in layout.

#FIG. 1 is a plan view of the bottom part of the mold pertaining to one embodiment of the apparatus for producing semiconductor in this invention.

#FIGS. 2a to 2c are sectional views of the mold, with the top part and the bottom part closed, on the line A--A in FIG. 1. FIG. 2a is a sectional view, with the cavities not yet filled with a resin. FIG. 2b is a sectional view, with the cavities being filled with a resin. FIG. 2c is a sectional view, with the cavities filled with a resin.

#FIG. 3 is a plan view of the bottom part of the mold pertaining to another embodiment of the apparatus for producing semiconductor in this invention.

#The present invention provides a mold which has a plurality of pots, runners independently connected to said pots, and a plurality of cavities serially connected to the end of each runner. The advantage of this mold over the one-pot mold is that the runners are very short, the resin flow in the runner is small, and the pressure loss of flowing resin is small.

#In an experiment with a mold in which one cavity is connected to each runner, it was confirmed that the pressure loss in the multipot system is only one-tenth that in the one-pot system having the same number of cavities. The experimental result is also true of molding with a mold having a plurality of pots, independent runners connected to each pot, and a plurality of cavities connected to the end of each runner. The pressure loss in such a mold is much lower than that in the one-pot system. Therefore, the molding with such a mold results in none of molding defects attributable to the increased pressure loss and improves the use efficiency of resin to a great extent.

#The embodiments of this invention are described in more detail with reference to FIGS. 1 to 5.