Epoxy resin sealing material for molding semiconductor chip and

Details Epoxy resin sealing material for molding semiconductor chip and Epoxy resin sealing material for molding semiconductor chip and

1999-03-10

2000-09-19

Dawson, Robert

Plastic and nonmetallic article shaping or treating: processes

Forming articles by uniting randomly associated particles

Agitating to form larger particles

523403, 523466, 525481, B29B 908

Patent

active

061207160

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND ART

1. Field of the Invention
The present invention is directed to an epoxy resin encapsulating material for molding in a semi-conductor chip and method of preparing the same.
2. Description of the Prior Art
Encapsulation of semiconductor chips has been made by a transfer molding using so-called tablets of an encapsulating composition composed of an epoxy resin, a curing agent, and an inorganic filler. The tablets are prepared by the steps of kneading the encapsulating composition and processing the same into a semi-cured body in the form of a sheet or wire, pulverizing the solid body into granules followed by being compacted into a cylindrical form. Thus prepared tablets are fed in a pot of a transfer-molding device and are forced into a mold cavity where they are molded to surround the semiconductor chip. Nowadays, there is proposed for enhancing encapsulation quality to use a multi-pot transfer molding device in which a plurality of pots are provided to encapsulate a plurality of the semiconductor chips at once with reduced length of runner leading from the pot to the associated mold cavity. As the number of the pots increases, the size of the tablets are required to be reduced to give the sufficient number of the tablets into each pot. In this respect, it is envisaged to utilize the pulverized granules of the encapsulating composition prior to being compacted into the tablet.
However, the granules after being pulverized from the semi-cured epoxy composition inherently includes a number of minute particles which are very likely to clog passages for supplying the encapsulating material to a metering section of the transfer molding device and for supplying it to the pots, thereby failing to supply a sufficient amount of the material to the mold cavity with attendant poor encapsulation. Such minute particles have a tendency to adhere to the large granules, they are difficult to be filtered out by the use of a sieve and are easily separated from the large granules when subjected to vibrations applied in the course of feeding the granules to the pot and/or the molding cavity. Further, the granules may be chipped at their corners when subjected to the vibrations to add resulting minute particles.
Even by the use of the tablets, the minute particles are easily separated from the tablets when subjected to the vibration while being fed to the pots and/or the cavities, thereby causing undesired clogging of the passages to the cavities.
In view of the problems, it is demanded to provide the epoxy encapsulating material in the form of the granules which can successfully avoid to clog the passages of the material in the transfer molding device.


SUMMARY OF THE INVENTION

The above problem has been solved in the present invention which provides an improved epoxy resin encapsulating material for molding in the semiconductor chip and method of preparing the same. The epoxy resin encapsulating material in accordance with the present invention has constituents of an epoxy resin, a curing agent, an inorganic filler, and a release agent and consists of 99 wt % or more of granules having a diameter of 0.1 to 5.0 mm and 1 wt % or less of minute particles having a diameter of less than 0.1 mm. The mass of the epoxy resin encapsulating material is characterized to exhibit an angle of slide of 20 to 40.degree., which demonstrates good flowability free from clogging the passage leading to the mold cavity, thereby assuring enhanced encapsulation quality. When the minute particles having a diameter of less than 0.1 mm are included in an amount of more than 1 wt % or the granules having a diameter of 0.1 mm to 5.0 mm are inclued in an amount of less than 99 wt %, the material is likely to clog the passage. Also, such clogging of the material is likely to occur with the use of the material having the angle of slide of more than 40.degree.. Although it may be possible to prepare the encapsulating material having the angle of slide of less than 20.degree., the preparation takes a long period of time and is not practical f

REFERENCES:
patent: 4137188 (1979-01-01), Uetake et al.

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