Stock material or miscellaneous articles – Composite – Of epoxy ether
Reexamination Certificate
2000-06-29
2002-01-15
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of epoxy ether
C428S620000, C209S217000, C209S219000, C209S228000, C425S215000, C264S211120, C427S096400
Reexamination Certificate
active
06338903
ABSTRACT:
TECHNICAL FIELD
This invention relates to a resin composition for semiconductor encapsulation not containing metal powder coated with a resin, ultra-fine metal powder, metal powder having low magnetism, etc, and a method and apparatus for producing such a resin composition. The present invention relates also to a resin-sealed semiconductor device using such a resin composition.
BACKGROUND ART
Conventional semiconductor devices are fabricated by packaging a semiconductor device onto a lead frame as a substrate and molding other portions with a resin, as is well known in the art. Recent down-sizing electronic appliances has created a demand for a reduction in the size and thickness, and higher performance of, semiconductor devices. Miniaturization of semiconductor devices, for example, has been mainly promoted by improvements in lead frames and molding resins. In line with this trend, a TSOP (Thin Small Outline Package) having a reduced thickness and QFP (Quad Flat Package) to cope with a multi-pin structure have been developed. A ball grid array (BGA) type package and a chip size package (CSP) have been developed to cope with the problems that the package size becomes greater with the increase of the number of pins and handling of package becomes more difficult as the pitch of external leads becomes smaller.
A resin composition, containing an epoxy resin as a main agent and inorganic fillers such as molten silica, has been generally used as a molding resin in the fabrication of the semiconductor devices described above. Such a resin composition is generally produced in the form of powder and particles through a series of unit operations of melt-kneading, pulverization, etc, of the mixture of starting materials such as epoxy resin, a curing agent, an inorganic filler, and so forth. More concretely, the resin composition in the powdery particle form is produced in the following way. The selected starting materials are mixed and the resulting mixture is molten, kneaded and cooled by metallic apparatuses such as a roll, an extruder, a kneader, etc. The mixture is thereafter pulverized by a pulverizing mill, a grinding mill, and so forth. When the powdery particles are produced through such a series of unit operations, however, the problem develops in that conductive metal powder originating from the metal material of the production apparatuses used mixes into the powdery particles.
Even though the mixing amount may be small, the conductive metal powder contained in the sealing resin composition can exert great influences on performance of the resulting semiconductor device. Chip size packages (CSP), for example, are produced by forming Cu bumps for external terminals by plating on a semiconductor wafer, applying resin molding by using a molding resin composition, forming solder balls on the Cu bumps and dicing the resulting processed semiconductor wafer into discrete semiconductor devices. In the resulting package, very fine wires having a wiring width/wiring gap =10 &mgr;m/10 &mgr;m are applied to the semiconductor wafer, and the thickness of the resin composition layer for molding the spaces between the wires is about 80 to about 120 &mgr;m. If any limited voids are contained in the resin composition layer, reliability of the semiconductor devices drops. Moreover, when a conductive metal powder exists in the mixture, the wires are short-circuited and this invites breakage of the device. In the case of a QFP, the gap of wire bonding tends to become smaller with the increase of the number of I/O pins. Therefore, the presence of the conductive metal powder contained in the sealing resin composition, if any, results in a remarkable drop in the reliability of the semiconductor devices.
In the CSP described above and in the QFP having wire bonding of a small pitch, and furthermore, in resin molded semiconductor devices using so-called “lead frame” or “TAB tape”, a semiconductor molding resin composition not containing conductive metal powder has therefore been desired to further improve device reliability.
When conductive metal powder is contained in the molding resin composition used for the fabrication of the semiconductor devices, it is a customary practice to insert a magnetic rod into the powder of the resin composition produced, and to stir the powder to remove the metallic powder. Though this method is effective for removing a metal powder having a relatively large size and a ferromagnetic metal powder, it is not sufficient to remove the metal powder having a relatively small particle size or the magnetic powder having relatively low magnetism. It has therefore been desired to efficiently separate and remove not only the metal powder having a large particle size and the ferromagnetic metal powder but also the metal powder having a smaller particle size and the metal powder having low magnetism.
Japanese Unexamined Patent Publication (Kokai) No. 9-173890 discloses a drum type metal classification-recovering apparatus for separating and recovering any foreign metal having magnetic property (iron dust, iron powder, etc) contained as a mixture in the powder of a resin pellet, or the like, although the technology of this reference is not directed particularly to remove the metal powder from the molding resin composition used for the fabrication of the semiconductor devices. The “Prior Art” of this Japanese Unexamined Patent Publication (Kokai) No. 9-173890 illustrates a drum type metal classification-recovering apparatus
60
shown in FIG.
1
. Reference numeral
61
in
FIG. 1
denotes a case, and a cylindrical non-magnetic drum
63
having a built-in semi-circular cylindrical magnetic drum
62
is turnably disposed inside the case
61
. Two scrapers
71
are fitted at symmetrical positions on the surface of the non-magnetic drum
63
. A hopper
64
for receiving a raw material
65
to be processed, a guide plate
66
for guiding the raw material
65
and a damper
67
for continuously supplying a suitable amount of the raw material
65
to the magnetic drum
62
are provided above the case. A partition member
72
is disposed at the lower part of the case, and a raw material discharge port
69
and a discharge port
73
for foreign metal are provided on both sides of the partition member
72
.
FIG. 2
shows a magnetic circuit construction of the non-magnetic drum
63
shown in
FIG. 1. A
substantially semi-circular magnetic member
74
is fixed to a shaft
78
through an arm
77
. Permanent magnets
75
are magnetized in a thickness-wise direction so that the portion thereof on the side of the non-magnetic drum
63
constitutes the N pole. Permanent magnets
76
are magnetized in the thickness-wise direction so that the portion thereof on the side of the non-magnetic drum
63
constitutes the S pole. These permanent magnets
75
and
76
are arranged alternately and equidistantly on the outer peripheral surface of the magnetic member
74
that is made of a steel. Thus, both permanent magnets
75
and
76
constitute a magnetic circuit through the magnetic member
74
. In other words, both permanent magnets
75
and
76
constitute a magnetic circuit in which the magnetic flux a flowing out from the N poles of the permanent magnet
75
generates the magnetic field on the surface of the non-magnetic drum
63
, permeates through the foreign metal
70
having a magnetic property, magnetically attracts the foreign metal
70
and returns to the S pole of the permanent magnet
76
.
In the drum type metal classification-recovering apparatus
60
, the main raw material
68
, as non-magnetic material inside the raw material
65
that is charged from the hopper
64
, is not affected by the magnetic force generated from the magnetic drum
62
. Therefore, the raw material
68
falls freely due to its own weight, and is discharged from the raw material discharge port
69
. On the other hand, the foreign metal
70
having magnetic property contained as mixture in the raw material
65
are affected by the magnetic force generated from the magnetic drum
62
and are attracted to the surfac
Takigawa Yukio
Yano Ei
Armstrong Westerman Hattori McLeland & Naughton LLP
Feely Michael J
Fujitsu Limited
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