U.S. patent application number 10/866824 was filed with the patent office on 2004-11-11 for semiconductor chip molding apparatus and method of detecting when a lead frame has been improperly positioned in the same.
Invention is credited to Koo, Hee-Mo, Lee, Sung-Soo, Park, Kyung-Soo.
Application Number | 20040222567 10/866824 |
Document ID | / |
Family ID | 19712962 |
Filed Date | 2004-11-11 |
United States Patent
Application |
20040222567 |
Kind Code |
A1 |
Park, Kyung-Soo ; et
al. |
November 11, 2004 |
Semiconductor chip molding apparatus and method of detecting when a
lead frame has been improperly positioned in the same
Abstract
A semiconductor chip molding apparatus includes an upper platen
including an upper mold, a lower platen including a lower mold
having a molding block configured to receive a lead frame, a
controller, and an electrical detector for forming an electrical
circuit between the controller and the lead frame when the lead
frame is oriented improperly on the lower mold. A low-level test
voltage is imparted to at least the lower mold. As a result, an
electrical signal will flow from the detecting block when the lead
frame rests on the detecting block. When such a signal is detected,
therefore, the lead frame is determined as having been improperly
set on the molding block. The signal generated is detected by a
controller and used thereby to interrupt the operation of the
molding apparatus.
Inventors: |
Park, Kyung-Soo;
(Cheonan-city, KR) ; Lee, Sung-Soo; (Cheonan-city,
KR) ; Koo, Hee-Mo; (Asan-city, KR) |
Correspondence
Address: |
VOLENTINE FRANCOS, & WHITT PLLC
ONE FREEDOM SQUARE
11951 FREEDOM DRIVE SUITE 1260
RESTON
VA
20190
US
|
Family ID: |
19712962 |
Appl. No.: |
10/866824 |
Filed: |
June 15, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10866824 |
Jun 15, 2004 |
|
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|
10125402 |
Apr 19, 2002 |
|
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|
6776598 |
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Current U.S.
Class: |
264/406 ;
257/E21.504 |
Current CPC
Class: |
B29C 45/842 20130101;
B29C 45/14655 20130101; H01L 2924/0002 20130101; B29C 43/18
20130101; B29C 43/58 20130101; H01L 21/565 20130101; B29C 43/36
20130101; H01L 2924/0002 20130101; H01L 2924/00 20130101 |
Class at
Publication: |
264/406 |
International
Class: |
B29C 043/18 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 7, 2001 |
KR |
2001-47564 |
Claims
1-6. (Cancelled).
7. A method for use in operating an inset-molding apparatus,
comprising: setting a metal part to be inset-molded on a lower mold
of the molding apparatus, the lower mold defining at least one mold
cavity; providing at least one electrically conductive detecting
block disposed adjacent said lower mold, the at least one
electrically conductive block being electrically insulated from at
least the lower mold; subsequently imparting a voltage to at least
one component of the apparatus, that includes the lower mold;
subsequently detecting whether an electrical signal flows from the
detecting block.
8. The method of claim 7, and further comprising determining that
the metal part to be inset-molded has been positioned improperly on
the lower mold when an electrical signal is detected as flowing
from the detecting block.
9. The method of claim 8, and wherein an operation of the molding
apparatus is interrupted when the electrical signal is detected
from the detecting block.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to inset-molding. More
specifically, the present invention relates to a semiconductor chip
molding apparatus and to a method of detecting whether a lead frame
is positioned properly in the same.
[0003] 2. Description of Related Art
[0004] The manufacturing of semiconductor devices, known as chip
packages, includes an assembly method in which chips are packaged
once they have undergone an electrical die sorting (EDS) process in
which individual chips having certain electrical and physical
characteristics are sorted. Hence, only non-defective chips are
packaged.
[0005] The assembly method includes a die bonding process of
attaching the non-defective chip on a pad of a lead frame, a wire
bonding process of electrically connecting bonding pads of the chip
to inner lead tip of the lead frame via connector wires, a molding
process of encapsulating the chip using an epoxy molding compound
so as to protect the chip, the connector wires, the inner leads,
and so on, and a forming process of finalizing the form of the chip
package so that the chip package may be mounted on a printed
circuit board (PCB).
[0006] The molding process is performed by a semiconductor molding
apparatus. In this apparatus, an epoxy molding compound is heated
and pressurized to assume a molten state. The molten compound is
then injected into molding cavities to encapsulate semiconductor
chips on lead frames set in position in the cavities.
[0007] The conventional semiconductor chip molding apparatus also
has a sensing unit that determines whether the lead frames are
properly positioned in the apparatus before the semiconductor chips
are encapsulated with the epoxy molding compound. Thus, the sensing
unit attempts to ensure that the molding process is performed
properly.
[0008] FIG. 1 is a cross-sectional view of the conventional
semiconductor chip molding apparatus.
[0009] Referring to FIG. 1, the conventional semiconductor chip
molding apparatus 90 includes a lower platen 70, and an upper
platen 80 opposed to the lower platen 70. A lower mold 50 is
integrated with the lower platen 70, and an upper mold 60 is
integrated with the upper platen 80.
[0010] The lower mold 50 includes a plurality of locater pins 53 at
the periphery thereof. The locater pins 53 guide a lead frame 20
into position on the lower mold 50. A port block 55 is disposed at
a central portion of the lower mold 50. The molding resin, such as
an epoxy molding compound, is supplied through the port block 55
after the lead frame 20 has been set on the lower mold 50.
[0011] As mentioned above, the conventional semiconductor chip
molding apparatus 90 further includes a sensing unit to determine
whether the lead frame has been properly set on the lower mold 50.
The sensing unit includes a sensing plate 57 and an approaching
sensor 65. The sensing plate 57 and the approaching sensor 65 are
disposed on corresponding portions of the lower platen 70 and the
upper platen 80, respectively.
[0012] After the lead frame 20 is set on the lower mold 50, the
upper platen 80 moves down until it contacts the port block 55 on
the lower platen 70. During this time, the approaching sensor 65
senses the sensing plate 57 and calculates the distance C between
the approaching sensor 65 and the sensing plate 57 to determine
whether the lead frame 20 is properly set on the lower mold 50.
When the calculated distance C between the lower mold 50 and the
upper mold 70 is equal to the thickness d of the port block 55, the
lead frame 20 is regarded as being properly set on the lower mold
50. On the other hand, when the distance C between the lower mold
50 and the upper mold 70 is greater than the thickness d of the
port block 55, the lead frame 20 is regarded as being improperly
set on the lower mold 50.
[0013] However, the conventional semiconductor chip molding
apparatus has the following disadvantages.
[0014] First, the lead frame 20 can be detected as being improperly
set on the lower mold 50 only when the lead frame 20 is disposed on
the port block 55 as shown in portion B of FIG. 1. In other words,
it is impossible to determine when the lead frame 20 has been set
on the locater pins 53 as shown in portion A of FIG. 1. This is
because the locater pins 53 penetrate the lead frame 20 under the
pressure of the upper mold 60. As a result, the locater pins 53
seem as though they are properly inserted into side rail holes (850
in FIG. 3) of the lead frame 20. Therefore, even though the lead
frame 20 is improperly set on the lower mold 50, the lead frame 20
is regarded by the sensing unit as being properly set on the lower
mold 50.
[0015] In addition, even when the lead frame 20 has been placed
over the port block 55 as shown in portion B of FIG. 1, the sensing
unit can hardly detect the improper positioning of the lead frame
20 because the lead frame 20 is very thin, e.g., is only 5 mil to
10 mil thick.
[0016] Moreover, epoxy molding compound scrap, produced in the
previous molding process, remains on the lower mold 50. The epoxy
molding compound scrap affects the ability of the sensing unit to
detect whether the lead frame 20 is properly set on the lower mold
20.
[0017] In the conventional semiconductor chip molding apparatus,
the lead frame 20 is regarded as being improperly set on the lower
mold 50 when the epoxy molding compound scrap has a thickness of
more than 0.3 mm. However, the conventional semiconductor chip
molding apparatus is calibrated to detect epoxy molding compound
scrap having a thickness of more than 0.5 mm for the purpose of
preventing the epoxy molding compound scrap from producing an
abnormal operation. Thus, the ability of the apparatus to determine
whether the lead frame is properly set on the lower mold is
nominal. Consequently, the manufacturing yield is poor.
SUMMARY OF THE INVENTION
[0018] An object of the present invention is to overcome the
above-described problems and limitations of the prior art. More
specifically, it is one object of the present invention to provide
a semiconductor chip molding apparatus that can accurately and
surely detect whether a lead frame is properly set in position. It
is another object of the present invention to provide an
inset-molding apparatus having an improved manufacturing yield.
[0019] In order to achieve the above object, the molding apparatus
comprises an upper platen including an upper mold, a lower platen
including a lower mold having a molding block defining at least one
mold cavity; a controller that controls an operation of the
semiconductor chip molding apparatus; and an electrical detector
for forming an electrical circuit between the controller and the
lead frame or other metal part to be inset-molded when the lead
frame or metal part is oriented a certain way, i.e., improperly, on
the lower mold.
[0020] The detector includes at least one detecting block
positioned adjacent the molding block so as to contact the lead
frame when the lead frame is improperly set on the molding block.
The detecting block is electrically insulated from components of
the molding apparatus, including the lower mold. A detecting wire
connects the detecting block to the controller and transfers the
electrical signal to the controller.
[0021] The detector further includes a connecting block connected
to the detecting block. The connecting block including a conductive
spring or a screw dispsoed in contact the detecting block so as to
transfer an electrical signal from the detecting block to the
controller.
[0022] Another object of the present invention is to provide a
method for use in operating an inset-molding apparatus, in
particular, a method of operating a semiconductor chip molding
apparatus, which accurately detects when a metal part such as a
lead frame to be inset-molded is improperly positioned over the
mold cavity.
[0023] The method comprises: setting the lead frame or other metal
part to be inset-molded on a conductive lower mold of the molding
apparatus; providing at least one electrically conductive detecting
block adjacent the lower mold, and electrically insulating the at
least one electrically conductive block from at least the lower
mold; and subsequently imparting a voltage to at least the lower
mold.
[0024] As a result, an electrical signal will flow from the
detecting block when the lead frame or other metal part to be
insert-molded rests on the detecting block. When such a signal is
detected, therefore, the lead frame or other metal part is
determined as having, for example, been improperly set on the
molding block. The signal generated is detected by a controller and
thereby used to control the further operation of the apparatus. In
particular, the controller interrupts the operation of the molding
apparatus when the monitoring of the detecting block for an
electrical signal indicates that the part to be inset-molded is
mis-positioned on the molding block relative to th mold cavity.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] These and other objects, features and advantages of the
present invention will become more apparent from the following
detailed description of the preferred embodiments thereof made with
reference to the accompanying drawings, in which like reference
numerals denote like parts, and of which:
[0026] FIG. 1 is a cross-sectional view of a conventional
semiconductor chip molding apparatus;
[0027] FIG. 2 is a schematic diagram of a semiconductor chip
molding apparatus according to the present invention;
[0028] FIG. 3 is a perspective view of a molding unit according to
the present invention;
[0029] FIG. 4 is a cross-sectional view taken along line IV-IV of
FIG. 3;
[0030] FIG. 5 is a plan view of a portion of the molding unit
showing a state in which a lead frame is oriented properly on the
molding block; and
[0031] FIG. 6 is a similar view showing a state in which the lead
frame is oriented improperly on the molding block.
DETAILED DESCRIPTION OF PREFFERED EMBODIMENTS
[0032] Referring now to FIG. 2, the semiconductor chip molding
apparatus 900 of the present invention includes a loading portion,
a molding portion, an unloading portion, and a controller 700.
[0033] The loading portion serves to load a lead frame onto the
molding portion, and includes a lead frame supplying unit 100 for
supplying a lead frame 800 (see FIG. 3), a tablet unit 200 for
supplying a molding resin, such as an epoxy molding compound, in
mass, and a loader unit 300 for transferring the lead frame 800
from the lead frame supplying unit 100 and the molding resin from
the tablet unit 200 to the molding portion, respectively.
[0034] The molding portion includes a molding unit 400 for
encapsulating the lead frame 800 in package form using the molding
resin, and a driving unit (not shown) for driving the molding unit
400 meaning that it appropriately pressurizes and heats the molding
resin in the molding unit 400.
[0035] The unloading portion includes an unloading unit 500 for
unloading the packaged lead frame 800 from the molding unit 400,
and a stacking unit 600 for sequentially stacking the packaged lead
frames 800 unloaded by the unloading unit 500.
[0036] The controller 700 controls all of the operating equipment
of the semiconductor chip molding apparatus of FIG. 1, and stops
the operation of the semiconductor chip molding apparatus 900 when
the lead frame 800 is improperly set on the molding unit 400 as
shown in FIG. 6.
[0037] Referring now to FIG. 3, the molding unit 400 includes a
lower platen 420 and an upper platen 460. A lower mold 440 is
secured to the lower platen 420, and an upper mold 480 opposed to
the lower mold 440 is secured to the upper platen 460.
[0038] The lower mold 440 is made of a conductive material, and
includes a port block 444 for substantially supplying the molding
resin in mass, and a molding block 441 on which the lead frame 800
is set. The molding block 441 is located at both sides of the lower
mold 440, whereas the port block 444 runs along the central part of
the lower mold 440. The port block 444 includes a ram port 445 on
which the molding resin is placed, and a runner 446 along which
molten molding resin flows into a mold cavity 442. The molding
block 441 includes a plurality of the mold cavities 442 that
accommodate a plurality of semiconductor chips mounted on the lead
frame 800.
[0039] Each of the cavities 442 has a shape corresponding to that
of the final package and includes a gate 443 that communicates with
a runner 446. The gate 443 serves as an inlet through which the
molten molding resin flows into the cavity 442.
[0040] The molding block 441 also includes a plurality of locater
pins 451 spaced along an outer edge thereof. The locater pins 451
are disposed at locations corresponding to side rail holes 850 of
the lead frame 800. When the lead frame 800 is properly set on the
molding block 441 as shown in FIG. 5, the locater pins 451 are
received in the corresponding side rail holes 850 of the lead frame
800.
[0041] The molding unit 400 also comprises lead frame detecting
means operable to generate a signal that stops the operation of the
semiconductor chip molding apparatus 900 when the lead frame 800 is
improperly set on the molding block 441. The lead frame detecting
means includes a detecting block 448 that effectively senses a
state of orientation of the lead frame 800, and a connection block
447 and a detecting wire 450 (see FIG. 5) which transfer an
electrical signal from the detecting block 448 to the controller
700.
[0042] The detecting block 448 is made of a conductive material.
Preferably, two detecting blocks 448 are oriented perpendicular to
the longitudinal direction of the lower mold 440, i.e.,
perpendicular to the lead frame 800, at opposite ends of the lower
mold 440. The detecting block 448 is electrically insulated from
the other components of the bottom half of the molding apparatus
400, such as the lower platen 420, the molding block 441, and the
port block 444. Preferably, an insulating member 449, comprising
any suitable electrical insulator, isolates the detecting block 448
(see FIG. 4). In this case, the insulating member 449 comprises a
lining of electrically insulating material interposed between the
port block 444 and the detecting block 448, between the molding
block 441 and the detecting block 448, and between the lower platen
420 and the detecting block 448. The insulating member 449 can be
formed unitarily with or separately from the detecting block
448.
[0043] The connecting block 447 is also made of a conductive
material and is electrically isolated from the lower mold 440 and
any component electrically conductively connected thereto.
Preferably, two such connecting blocks 447 are electrically
connected to the corresponding detecting blocks 448 via a
conductive connecting member 447a such as a metal spring or a
screw. The connecting member 447a serves as an electrical contact
that presses against the connecting block 447 when the lower mold
440 is attached to the lower platen 420. The detecting wire 450
shown in FIG. 5 is electrically connected to each detecting block
448 via only a connecting block 447, and is electrically connected
to the controller 700.
[0044] Hereinafter, the operation of the semiconductor chip molding
apparatus 900 and a method of detecting whether the lead frame has
been improperly set in position on the lower mold 440 will be
described with reference to FIGS. 2 to 6.
[0045] The lead frame 800 having semiconductor chips thereon is
stacked on the lead frame supplying unit 100. The loading unit 300
transfers the lead frame 800 from the lead frame supplying unit 100
to the molding block 441 of the molding unit 400. The loading unit
300 sets the lead frame 800 on the molding block 441 such the side
rail holes 850 of the lead frame 800 receive the locater pins 451.
At the same time, the loading unit 300 also transfers molding resin
to the ram port 445 of the port block 444. The port block has been
previously heated such that at this moment, the port block 444 has
a temperature of about 180.degree. C. Thus, the molding resin
becomes molten when it is placed on the ram port 445.
[0046] When the lead frame 800 is properly set on the molding block
441, the driving unit (not shown) exerts a predetermined driving
force on the lower platen 420 or the upper platen 460 of, for
example, about 3 tons. As a result, the lower mold 440 and the
upper mold 480 are forced together under a pressure of about 120
torr.
[0047] At this moment, the driving unit pushes the molten mold
resin out of the ram port 445 using a mechanical element, e.g., a
piston. The molten molding resin flows via the runner 446 into the
cavity 442 or, more specifically into the cavity formed by the
confronting molding blocks of the lower mold 440 and the upper mold
480.
[0048] The molten molding resin remains in the cavity 442 for a
predetermined time period until it is cured. Once the molding resin
is cured, the semiconductor chip is encapsulated. Subsequently, the
unloading unit 500 unloads the packaged lead frame 800 from the
molding unit 400 and transfers it to the stacking unit 600,
whereupon the molding process is complete.
[0049] Now, if the lead frame 800 transferred from the lead frame
supplying unit 100 by the loading unit 100 is set somewhat askew on
the molding block 441, i.e., improperly, the lead frame 800 rests
atop the locater pins 451 and the port block 444. In this case, the
lead frame 800 also contacts one or more of the detecting blocks
448. Therefore, the detecting block(s) 448 is/are electrically
connected to the lower mold 440 because the lead frame 800 is an
electrical conductor. That is, the lead frame 800 serves as a
switch for electrically connecting the lower mold 440 to the
detecting block 448.
[0050] A voltage is applied by a voltage source V across some point
on the semiconductor chip molding apparatus 900, except at the
detecting block 448. This test voltage is a low voltage for the
sake of safety. In particular, a voltage of about -24 volts is
applied to any one of several components of the semiconductor chip
molding apparatus 900 that include or are otherwise in an
electrical conductive relationship with the lower mold 440.
Therefore, a signal having a voltage of -24 volts will flow into
the controller 700 through the detecting block 448 and the
detecting wire 450 via locater pins 451 and/or port block 444, and
lead frame 800. Consequently, the controller 700 recognizes that
the lead frame 800 is improperly set on the molding block 441. The
controller 700 thus stops the operation of the semiconductor chip
molding apparatus 900.
[0051] As is clear form the description above, the semiconductor
chip molding apparatus according to the present invention can
accurately detect whether the lead frame is properly set on the
molding block, whereby the manufacturing yield can be improved.
[0052] Although the present invention has been particularly shown
and described with reference to the preferred embodiments thereof,
the form and details thereof may be changed in various ways, as
will be apparent by those of ordinary skill in the art, without
departing from the true spirit and scope of the invention as
defined by the appended claims.
* * * * *