U.S. patent application number 09/732672 was filed with the patent office on 2001-06-14 for article feeding apparatus.
This patent application is currently assigned to NGK Insulators, Ltd.. Invention is credited to Ohnishi, Takao, Takeuchi, Yukihisa, Tsuji, Hiroyuki.
Application Number | 20010003567 09/732672 |
Document ID | / |
Family ID | 18386165 |
Filed Date | 2001-06-14 |
United States Patent
Application |
20010003567 |
Kind Code |
A1 |
Takeuchi, Yukihisa ; et
al. |
June 14, 2001 |
Article feeding apparatus
Abstract
An apparatus for feeding semiconductor chips has a structural
body having grooves which serve respectively as parallel feed paths
for semiconductor chips, the feed paths corresponding to respective
quality levels of the semiconductor chips, the structural body
being made of partially stabilized zirconia. A stopper mechanism
for temporarily stopping semiconductor chips fed along the feed
paths comprises piezoelectric bodies disposed in the feed paths in
front of terminal walls of the feed paths. A counter mechanism for
counting semiconductor chips fed along the feed paths have
electrodes disposed in the feed paths near the terminal walls. The
apparatus serves as a feed system for floating articles with
ejected air and feeding the floated articles, and lends itself to
being automatized.
Inventors: |
Takeuchi, Yukihisa;
(Nishikamo-Gun, JP) ; Tsuji, Hiroyuki; (Nagoya,
JP) ; Ohnishi, Takao; (Nishikasugai-Gun, JP) |
Correspondence
Address: |
BURR & BROWN
PO BOX 7068
SYRACUSE
NY
13261-7068
US
|
Assignee: |
NGK Insulators, Ltd.
|
Family ID: |
18386165 |
Appl. No.: |
09/732672 |
Filed: |
December 8, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09732672 |
Dec 8, 2000 |
|
|
|
09212342 |
Dec 15, 1998 |
|
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|
6203250 |
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Current U.S.
Class: |
406/28 |
Current CPC
Class: |
H01L 21/67784 20130101;
B65G 51/03 20130101 |
Class at
Publication: |
406/28 |
International
Class: |
B65G 051/36 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 16, 1997 |
JP |
9-346,839 |
Oct 15, 1998 |
JP |
10-291133 |
Claims
What is claimed is:
1. An apparatus for floating articles with ejected air and feeding
the floated articles, comprising: at least one feed path for
feeding articles therealong in a feed direction, said feed path
comprising a groove; a first layer having side walls of said
groove; a second layer serving as a bottom wall of said groove and
having a plurality of air ejection holes defined therein; a third
layer having an air distribution passage for distributing air to
said air ejection holes; and a fourth layer serving as a bottom
surface of said air distribution passage; at least said second
layer being made of a ceramic material.
2. An apparatus according to claim 1, further comprising a stopper
mechanism positioned at a terminal end of said feed path, for
temporarily stopping an article fed along said feed path, said
stopper mechanism having at least a pair of piezoelectric
bodies.
3. An apparatus according to claim 1, wherein said first layer is
made of glass or synthetic resin.
4. An apparatus according to claim 3, further comprising a stopper
mechanism positioned at a terminal end of said feed path, for
temporarily stopping an article fed along said feed path, said
stopper mechanism having at least a pair of piezoelectric
bodies.
5. An apparatus according to claim 1, further comprising: a counter
mechanism disposed in said feed path, for counting articles fed
along said feed path; said counter mechanism having electrodes for
detecting a change in a voltage which is produced by a change in an
electrostatic capacitance between said electrodes when an article
passes over said electrodes.
6. An apparatus for feeding electronic parts, comprising: a
structural body having grooves which serve respectively as parallel
feed paths for electronic parts, said feed paths corresponding to
respective quality levels of the electronic parts, said structural
body being made of partially stabilized zirconia; a stopper
mechanism for temporarily stopping electronic parts fed along said
feed paths, said stopper mechanism comprising piezoelectric bodies
disposed in said feed paths in front of terminal walls of the feed
paths; and a counter mechanism for counting electronic parts fed
along said feed paths, said counter mechanism having electrodes
disposed in said feed paths near said terminal walls.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an article feeding
apparatus for feeding articles (various electronic parts such as
semiconductor chips) being fabricated to a next manufacturing
process or feeding completed articles to a next assembling
process.
[0003] 2. Description of the Related Art
[0004] Generally, production lines for articles (various electronic
parts such as semiconductor chips) often employ containers in the
form of upwardly open boxes for feeding a number of articles to a
next fabrication process or a storage chamber.
[0005] For feeding a number of electronic parts (hereinafter also
referred to as "workpieces") with a container along a production
line, the workpieces are randomly placed into the container, and
the container is automatically delivered to a next fabrication
process or a storage chamber by a belt conveyor or a feed arm.
[0006] If articles to be fed are small-size articles such as
electronic parts, then it is known to employ a feed path having a
number of small holes and ejecting air through these holes to feed
the articles.
[0007] According to the air-feeding process, a number of small-size
articles can smoothly be fed to a destination within a reduced
period of time while reducing foreign matter which would otherwise
tend to be attached to the articles.
[0008] The air-feeding process is carried out by a feeding
apparatus which is usually made of a metal such as aluminum or
steel to meet robustness requirements of the feeding apparatus.
However, it is not easy to form small air-ejection holes in the
metal panel of the feed path for controlling a floated state of
small articles to be fed. When the feeding apparatus is used for-a
long period of time, the feed path, which is in the form of a
groove, tends to be worn, and particles abraded off the feed path
are liable as foreign matter to the articles being fed.
SUMMARY OF THE INVENTION
[0009] It is therefore an object of the present invention to
provide an article feeding apparatus which has an automatized feed
system for floating and feeding articles of small dimensions in one
direction with air, and which can handle articles in a clean state
without producing foreign matter such as small dust particles.
[0010] According to the present invention, there is provided an
apparatus for floating articles with ejected air and feeding the
floated articles, comprising at least one feed path for feeding
articles therealong in a feed direction, the feed path comprising a
groove, a first layer having side walls of the groove, a second
layer serving as a bottom wall of the groove and having a plurality
of air ejection holes defined therein, a third layer having an air
distribution passage for distributing air to the air ejection
holes, and a fourth layer serving as a bottom surface of the air
distribution passage, at least the second layer being made of a
ceramic material. The ceramic material should preferably be, but
not necessarily limited to, partially stabilized zirconia for its
strength. The apparatus serves as a feed system for floating
articles with ejected air and feeding the floated articles, and
lends itself to being automatized.
[0011] Since the ceramic material can easily be shaped highly
accurately when formed, a plurality of small fluid ejection holes
each having a diameter ranging from several tens to several
hundreds .mu.m can be defined in the second layer for floating and
feeding articles of small dimensions. It is preferable to provide
at least three fluid ejection holes per feed area corresponding to
one article.
[0012] If the first layer having side walls of the groove is made
of a ceramic material, then it can be shaped accurately to small
dimensions. For example, if semiconductor chips each of a square
shape having a size of about 0.2 mm.times.0.2 mm is to be fed, then
grooves as feed paths can be defined in the first layer at a small
pitch of about 0.5 mm. The article feeding apparatus may be small
in size. If an insulative ceramic material is used, then electrodes
may easily be formed on the layers by printing or the like.
[0013] All the layers including the third and fourth layers may be
formed of a ceramic material. For example, if all the layers are
formed and sintered separately and then bonded into a unitary
assembly, then the unitary assembly is free of problems such as of
warpage or the like due to thermal expansion and shrinkage which
would otherwise occur if the layers are made of different
materials. Alternatively, formed sheets of the layers may be
laminated together and then sintered. This latter process is
preferable because no bonding process is required and the layers
can be manufactured inexpensively and handled cleanly.
[0014] In the article feeding apparatus, furthermore, the first
layer may preferably be made of glass or synthetic resin. If
electrodes of a metal material are formed on the surface of the
second layer which has been formed and sintered, the first layer to
be placed on the second layer and then sintered needs to be
sintered at a temperature lower than the melting point of the
second layer if the second layer is made of a ceramic material. In
view of this limitation, it is preferable to make the first layer
of glass or synthetic resin which has a low melting point, and to
print or coat a sheet of the first layer on the second layer on
which electrodes have been printed, and then sinter the sheet of
the first layer. Making the first layer of glass is preferable
because it is resistant to wear. The application of a sheet of the
first layer to the second layer is not limited to the printing or
coating process, but may be carried out by bonding a formed sheet
of glass or synthetic resin to the second layer with an adhesive.
The glass or synthetic resin is not limited to any particular
type.
[0015] The article feeding apparatus also has a stopper mechanism a
stopper mechanism positioned at a terminal end of the feed path,
for temporarily stopping an article fed along the feed path, the
stopper mechanism having at least a pair of piezoelectric bodies.
The piezoelectric bodies have upper ends held at a height slightly
lower than the height to which the articles are floated. When a
voltage is applied to the first piezoelectric body, it is deformed
to lift its upper end to such a height that the first piezoelectric
body becomes a barrier in the feed path. An article (first article)
which has been fed hits the barrier and is temporarily stopped.
Thereafter, the applied voltage is removed to allow the stopped
article to be fed to a downstream unloading position at the
terminal end of the feed path where the article will be unloaded.
The second piezoelectric body is positioned upstream of the first
piezoelectric body, and temporarily stops a next article (second
article) positioned behind (upstream of) the first article. One or
more second piezoelectric body may further be provided
upstream.
[0016] In conventional apparatus for feeding articles with air,
since air is ejected to feed the articles in one direction with no
control effected on the articles being fed, articles tend to be
held closely against each other at the terminal end of the feed
path and hence cannot easily be unloaded. Therefore, it has been
customary to unload semiconductor chips individually manually from
the conventional apparatus, and the feed system of the conventional
apparatus cannot be fully automatized.
[0017] According to the present invention, as described above, a
voltage is applied to the first piezoelectric body to reliably stop
a first article temporarily, and then removed to allow only the
stopped article to be fed to the downstream unloading position.
When only the first article is fed downstream to the unloading
position, a voltage is applied to the second piezoelectric body
positioned upstream of the first piezoelectric body for thereby
decelerate and stop the second article, which is thus prevented
from being continuously fed into overlapping relation to the first
article. Consequently, the first article can easily be unloaded at
the unloading position.
[0018] The article feeding apparatus further comprises a counter
mechanism disposed in the feed path, for counting articles fed
along the feed path, the counter mechanism having electrodes for
detecting a change in a voltage which is produced by a change in an
electrostatic capacitance between the electrodes when an article
passes over the electrodes. Count information from the counter
mechanism is used to automatize the article feeding apparatus.
[0019] Usually, the article feeding apparatus has as many grooves
as the number of quality levels of articles to be fed, for use as
feed paths. If these feed paths are associated with respective
article unloading units, then suitable counter mechanisms may be
combined with the respective article unloading units. However,
facility cost and installation space considerations have prevented
the feed paths from being associated with respective article
unloading units, but have actually allowed the feed paths to share
one or few article unloading units. Accordingly, articles belonging
to the respective quality levels cannot individually be counted.
According to the present invention, however, a voltage is
continuously applied between the electrodes of the counter
mechanism, and the electrostatic capacity between the electrodes
varies depending on whether an article passes over the electrodes
or not. Such a variation of the electrostatic capacity is detected
as a voltage change. Since the electrodes can easily be provided in
each of the feed paths, articles belonging to the respective
quality levels can individually be counted with ease. If the
counter mechanism is positioned at an intermediate position in each
of the feed paths, then the counter mechanism may be used as a
sensor for detecting when a certain number of articles remain
stagnant between the unloading position and the intermediate
position.
[0020] While being fed along the feed path, the preceding first
article is constantly pushed by and held against the following
second article, and hence these articles cannot reliably be
distinguished by the counter mechanism. Therefore, the counter
mechanism is placed in the unloading position at the terminal end
of the feed path where the preceding first article is reliably
separated from the following second article. The counter mechanism
thus positioned is effective in counting articles fed along the
feed path, without fail.
[0021] The above and other objects, features and advantages of the
present invention will become more apparent from the following
description when taken in conjunction with the accompanying
drawings in which preferred embodiments of the present invention
are shown by way of illustrative example.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a perspective view of an article feeding apparatus
according to the present invention;
[0023] FIG. 2 is a perspective view of a feed path of the article
feeding apparatus shown in FIG. 1;
[0024] FIG. 3 is a sectional perspective view taken along line
III-III of FIG. 2;
[0025] FIG. 4 is a plan view of the article feeding apparatus shown
in FIG. 1;
[0026] FIG. 5 is an enlarged fragmentary plan view of a region in
the vicinity of an end wall of the feed path shown in FIG. 4;
[0027] FIG. 6 is a cross-sectional view taken along line IV-IV of
FIG. 5;
[0028] FIG. 7 is a fragmentary perspective view of a piezoelectric
body according to a first embodiment;
[0029] FIG. 8 is a fragmentary perspective view of a piezoelectric
body according to a second embodiment; and
[0030] FIG. 9 is a fragmentary cross-sectional view taken along
line IX-IX of FIG. 4.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0031] As shown in FIG. 1, an article feeding apparatus 10 has a
plurality of parallel grooves serving as feed paths 12 for feeding
a number of semiconductor chips. The article feeding apparatus 10
has a structural body made of partially stabilized zirconia (PSZ),
which includes a region where the above grooves are defined.
[0032] The article feeding apparatus 10 serves to sort out
semiconductor chips according to their quality level. Specifically,
after semiconductor chips on wafers 14 are inspected for quality,
the wafers 14 are carried to the article feeding apparatus 10, and
the semiconductor chips are attracted one at a time under vacuum by
a robot 16a. Each of the semiconductor chips is delivered by the
robot 16a to one of the feed paths 12 depending on the quality
level of the semiconductor chip. Therefore, each of the feed paths
12 is loaded with and feeds successive semiconductor chips of a
certain quality level. The semiconductor chips that have arrived at
the terminal ends of the feed paths 12 are attracted under vacuum
by a robot 16b, and carried to and placed in cases 18a-18n assigned
to the respective quality levels. Thereafter, the cases 18a-18n are
delivered to a next process.
[0033] The article feeding apparatus 10 basically comprises a
mechanism for floating charged semiconductor chips, a mechanism
(propelling mechanism) for feeding floated semiconductor chips in a
feed direction along the feed paths 12, and a mechanism for
reliably removing semiconductor chips one at a time from the
terminal end of each of the feed paths 12. One of the feed paths
12, which are identical to each other, is illustrated in FIG.
2.
[0034] In FIG. 2, the feed path 12 is associated with a mechanism
for floating charged semiconductor chips 26, which mechanism is in
the form of a plurality of air ejection holes 20 defined vertically
in a feed panel of the feed path 12, for ejecting air upwardly
therethrough. The feed path 12 is associated with a mechanism
(propelling mechanism) for feeding floated semiconductor chips 26
in a feed direction, which mechanism is in the form of an air
blowing pipe 22 connected to an air supply system including an air
pump and a solenoid-operated valve (not shown). The air blowing
pipe 22 has a nozzle 24 mounted on its lower tip end for ejecting
air under a pressure of about 0.5 kgf/cm.sup.2 toward a
semiconductor chip 26 on the feed panel. The feed path 12 is also
associated with a mechanism for reliably removing semiconductor
chips 26 one at a time, which mechanism is in the form of a
plurality of air ejection holes 20 defined in the terminal end of
the feed path 12, remote from the air blowing pipe 22, for ejecting
air therethrough to float one at a time of the semiconductor chips
26, so that the floated semiconductor chip 26 can be attracted
under vacuum and smoothly fed by the robot 16b (see FIG. 1). As can
be seen from FIG. 2, the air ejection holes 20 defined in the
terminal end of the feed path 12 are provided at a greater density
than the air ejection holes 20 defined in the remainder of the feed
path 12.
[0035] An upstanding terminal wall 28 disposed at the terminal end
of the feed path 12 has a plurality of parallel vertical slits 30
defined therein. The slits 30 prevent foreign matter from being
accumulated against the upstanding terminal wall 28 and hence from
being applied to semiconductor chips 26 when they arrive at the
terminal end of the feed path 12.
[0036] Since the article feeding apparatus 10 is made of a ceramic
material, it is prevented from being unduly worn and producing
foreign matter as dust particles.
[0037] The mechanism (propelling mechanism) for feeding floated
semiconductor chips 26 in the feed direction may alternatively
comprise means for tilting downwardly the feed path 12 through a
predetermined angle with respect to the feed direction. When the
feed path 12 is tilted downwardly, floated semiconductor chips 26
are fed by gravity down the feed path 12.
[0038] The air ejection holes 20 may be defined obliquely in the
feed panel of the feed path 12 for ejecting air upwardly and toward
the feed direction therethrough. The air thus ejected from the air
ejection holes 20 impart a floating force and a propelling force to
semiconductor chips 26 in the feed path 12.
[0039] The mechanism for reliably removing semiconductor chips 26
one at a time may alternatively comprise means for designing a
planar shape of the feed path 12 in order to maximize the lift of
the semiconductor chips 26 near the terminal wall 28. Specifically,
the air ejection holes 20 defined in the terminal end of the feed
path 12 may be provided at the same density as the air ejection
holes 20 defined in the remainder of the feed path 12, and the
planar shape of the feed path 12 may be designed to make an amount
of air leaking through the gap between a semiconductor chip 26 and
the feed path 12 at the terminal end of the feed path 12 smaller
than the amount of air leaking through the gap between a
semiconductor chip 26 and the feed path 12 in the remainder of the
feed path 12.
[0040] To prevent foreign matter from being attached to
semiconductor chips 26, the terminal wall 28 may have protrusions
thereon projecting toward semiconductor chips 26, i.e., upstream in
the feed direction, so that the protrusions will be held in
point-to-point contact with a semiconductor chip 26 as it arrive at
the terminal end of the feed path 12.
[0041] As shown in FIG. 3, the structural body of the article
feeding apparatus 10 includes first, second, third, and fourth
layers 31a, 31b, 31c, 31d successively arranged downwardly. The
first through fourth layers 31a-31d are all made of partially
stabilized zirconia. The first through fourth layers 31a-31d may be
manufactured either by forming sheets of the ceramic material,
integrally joining the sheets, and sintering the joined sheets, or
by sintering separate sheets of the ceramic material and bonding
the sintered sheets together.
[0042] The first layer 31a has a plurality of parallel spaced
narrow grooves defined therein as the feed paths 12 by side walls
thereof. For example, if each of the semiconductor chips 26 is of a
square shape having a size of about 0.2 mm.times.0.2 mm, then the
narrow grooves as the feed paths 12 for feeding such semiconductor
chips 26 are defined at a pitch or center-to-center distance of
about 0.5 to 0.7 mm, the narrow grooves each having a width (W)
ranging from about 0.2 to 0.3 mm. The narrow grooves as the feed
paths 12 can be defined with high dimensional accuracy. Since the
feed paths 12 are very small in size, therefore, the article
feeding apparatus 10 may be small in size.
[0043] The second layer 31b, which serves as a bottom wall of each
of the feed paths 12, has a number of air ejection holes 20 defined
therein, and also has a plurality of electrodes 32a-32c supported
thereon which are electrically connected to a piezoelectric body
(described later on). Each of the air ejection holes 20 is of a
very small diameter, e.g., in the range from 10 to 120 .mu.m. The
electrodes 32a-32c may easily be printed on the second layer 31b.
The air ejection holes 20 are preferably provided at such a density
that three air ejection holes 20 are assigned to each semiconductor
chip 26.
[0044] The third layer 31c has a plurality of air distribution
passages 34 defined therein for distributing air to the air
ejection holes 20 in the second layer 31b. The air distribution
passages 34 extend parallel to each other along the feed paths 12
and are connected to respective air supply holes 36 defined in the
fourth layer 31d. The third layer 31c may instead have a single air
distribution chamber associated with all the feed paths 12.
[0045] The fourth layer 31d serves to provide bottom surfaces of
the air distribution passages 34. The air supply holes 36 in the
fourth layer 31d have upper ends opening into the air distribution
passages 34. The air supply holes 36 may be defined in side walls
of the third layer 31c, and the fourth layer 31d may be in the form
of a sheet with no holes defined therein.
[0046] The second layer 31b needs to be made of a ceramic material
such as partially stabilized zirconia. However, the third layer 31c
and the fourth layer 31d are not limited to the same ceramic
material as the second layer 31b though the third layer 31c and the
fourth layer 31d which are made of the same ceramic material as the
second layer 31b are free of problems such as of warpage or the
like due to thermal expansion and shrinkage.
[0047] If the electrodes 32a-32c are printed on the second layer
31b and the electrodes 32a-32c are made of a cermet material which
comprises a metal such as platinum and a ceramic material such as
partially stabilized zirconia diffused in the metal, then the first
layer 31a may be made of a ceramic material. If the electrodes
32a-32c are made of a metal such as gold or platinum, then the
first layer 31a may be produced by printing a glass material and
then sintering the printed glass material or by bonding a synthetic
resin. This is because if the first layer 31a were made of a
ceramic material, it would melt the metal of the electrodes 32a-32c
when the first layer 31a would be sintered.
[0048] A stopper mechanism used in the article feeding apparatus 10
will be described below.
[0049] As shown in FIG. 4, the article feeding apparatus 10 has ten
grooves as feed paths 12 which correspond respectively to the
quality levels of semiconductor chips 26. Semiconductor chips 26
are charged into the article feeding apparatus 10 from a left-hand
charging area in FIG. 4, and floated and fed along the feed paths
12 toward their terminal ends at a right-hand area in FIG. 4. Each
of the feed paths 12 has a length of about 300 mm, and has first
and second piezoelectric bodies 38a, 38b at the terminal end of the
feed path 12. The first and second piezoelectric bodies 38a, 38b
serve as the stopper mechanism.
[0050] Each of the first and second piezoelectric bodies 38a, 38b
preferably comprises a film of piezoelectric ceramic material, but
may comprise a film of electrostrictive or ferroelectric ceramic
material. The ceramic material used may be a material which needs
to be either polarized or not. The first and second piezoelectric
bodies 38a, 38b are fabricated by printing the above ceramic
material on a formed body of the second layer 31b and then
sintering the printed ceramic material together with the formed
body of the second layer 31b. The ceramic material may be lead
zirconate, lead titanate, lead magnesium niobate, nickel lead
niobate, lead zinc niobate, or the like, which may be used singly
or in combination. Preferably, the first and second piezoelectric
bodies 38a, 38b are preferably made mainly of lead zirconate, lead
titanate, and lead magnesium niobate because they have a high
electromechanical coupling coefficient and a high piezoelectric
constant, are less reactive with the material of the article
feeding apparatus 10 at the first and second piezoelectric bodies
38a, 38b are sintered, and can stably produce a desired
composition.
[0051] As shown in FIG. 5, the first piezoelectric body 38a is
spaced upstream of the terminal wall 28 by a distance which is
slightly greater than the size of a semiconductor chip 26, and the
second piezoelectric body 38b is spaced upstream of the first
piezoelectric body 38a is spaced upstream of the terminal wall 28
by a distance which is slightly greater than the size of a
semiconductor chip 26. The second layer 31b supports thereon
individual electrodes 32a, 32b and a common electrode 32c which
allow the first and second piezoelectric bodies 38a, 38b to form an
electric circuit. The electrodes 32a-32c are connected to a DC
power supply. The common electrode 32c connected to the first and
second piezoelectric bodies 38a, 38b has an upper end held in a
position which is about 3-5 .mu.m lower than the height to which
the semiconductor chip 26 is floated. Electrodes 40a, 40b of a
counter mechanism are disposed in the vicinity of the terminal wall
28. The electrodes 40a, 40b will be described later on.
[0052] The electrodes 32a-32c are made of an electrically
conductive metal which is solid at normal temperature, such as
gold, platinum, iridium, tungsten, tantalum, tin, silver, rhodium,
or the like, which may be used singly or in combination.
Alternatively, the electrodes 32a-32c may be made of a cermet
material which comprises the same ceramic material as the first and
second piezoelectric bodies 38a, 38b or the third layer 31b that is
diffused in the above material. The electrodes 32a-32c may be
sintered of a material of a high melting point together with the
first and second piezoelectric bodies 38a, 38b, taking into account
the melting point of the material of the first and second
piezoelectric bodies 38a, 38b, or may be produced separately after
the first and second piezoelectric bodies 38a, 38b have been
sintered of a material of a low melting point.
[0053] As shown in FIG. 6, the second piezoelectric body 38b is
sandwiched and bonded between the common electrode 32c and the
individual electrode 32b. In FIG. 6, the semiconductor chip 26 is
fed to a position above the second piezoelectric body 38b. The
second layer 31b comprises a thin film having a thickness of about
20 .mu.m, and is sufficiently flexible with opposite ends clamped
between the first layer 31a and the third layer 31c.
[0054] As shown in FIG. 7, the first and second piezoelectric
bodies 38a, 38b may be disposed on the second layer 31b, and the
individual electrodes 32a, 32b, which are comb-shaped, and the
common electrode 32c, which is also comb-shaped, may be disposed in
spaced interdigitating relation to each other on the first and
second piezoelectric bodies 38a, 38b. Alternatively, as shown in
FIG. 8, the individual electrodes 32a, 32b, which are comb-shaped,
and the common electrode 32c, which is also comb-shaped, may be
disposed in spaced interdigitating relation to each other on the
second layer 31b, with the first and second piezoelectric bodies
38a, 38b disposed in the gap between the individual electrodes 32a,
32b and the common electrode 32c.
[0055] Operation of the stopper mechanism will be described
below.
[0056] As shown in FIG. 9, when a voltage is applied to the first
piezoelectric body 38a, it is mechanically deformed into a barrier
having an increased height in the feed path. When a floated
semiconductor chip 26a collides with the barrier, the semiconductor
chip 26a which has traveled to a position near the terminal end of
the feed path is temporarily stopped. Then, the applied voltage is
removed, allowing the first piezoelectric body 38a to return to an
original height thereof slightly lower than the height of the
floated semiconductor chip 26a. The stopped semiconductor chip 26a
is now permitted to travel further downstream to an unloading
position at the terminal end of the feed path. After the
semiconductor chip 26a has been fed to the unloading position, a
voltage is applied again to the first piezoelectric body 38a to
stop a next semiconductor chip 26b. The above cycle of operation
will subsequently be repeated.
[0057] When the first piezoelectric body 38a returns to the
original height, permitting the semiconductor chip 26a to travel
further downstream to the unloading position, a voltage is applied
to the second piezoelectric body 38b to impose frictional forces on
the surface of the next semiconductor chip 26b which is in contact
with the second piezoelectric body 38b thereby to decelerate and
stop the semiconductor chip 26b for preventing the semiconductor
chip 26b from being directly fed to the unloading position and
hence overlapping the semiconductor chip 26a. Therefore, whereas a
voltage is repeatedly applied and removed from the first
piezoelectric body 38a in certain periodic cycles, a voltage is
applied to the second piezoelectric body 38b during periods of time
in which no voltage is applied to the first piezoelectric body 38a
and marginal periods before and after those periods of time. Since
the second layer 31b on which the first and second piezoelectric
bodies 38a, 38b are mounted is sufficiently flexible, when voltages
are applied to the first and second piezoelectric bodies 38a, 38b,
the first and second piezoelectric bodies 38a, 38b are allowed to
be deformed effectively without being unduly constrained by the
second layer 31b.
[0058] For reliably allowing the first and second piezoelectric
bodies 38a, 38b to operate reliably as described above, the
original thickness (height) of the first and second piezoelectric
bodies 38a, 38b should preferably be in the range from about 10 to
30 .mu.m. The surface of the second piezoelectric body 38b should
preferably be coated with highly wear-resistant glass or resin film
for increasing frictional forces exerted thereby to the
semiconductor chip 26b.
[0059] The counter mechanism in the article feeding apparatus 10
will be described below.
[0060] The counter mechanism is positioned in alignment with the
first piezoelectric body 38a or the second piezoelectric body 38b
in each of the feed paths 12. As shown in FIGS. 4 and 5, the
electrodes 40a, 40b of the counter mechanism are disposed at the
terminal end of each of the feed paths 12 near the terminal wall 28
and transversely spaced from each other. The electrodes 40a, 40b
are electrically connected to respective conductors 42.
[0061] Alternatively, as shown in FIG. 6, the common electrode 32c
may be used as one of the electrodes of the counter mechanism, and
an electrode 44 may be mounted on the first layer 31a over the
common electrode 32c for use as the other electrode of the counter
mechanism. With this arrangement, some of the existing electrodes
and circuit may be used as part of the counter mechanism. Further
alternatively, as shown in FIG. 4, the electrodes of the counter
mechanism may be located at an intermediate position in each of the
feed paths 12, e.g., at the ninth semiconductor chip 26, as counted
upstream (away from the terminal wall 28) from the terminal end of
each of the feed paths 12, of a series of nine semiconductor chips
26 staying in the feed path 12.
[0062] The electrodes 40a, 40b of the counter mechanism may be made
of the same material and may be manufactured in the same manner as
the electrodes 32a-32c connected to the first and second
piezoelectric bodies 38a, 38b, or may not be limited to the same
material as the electrodes 32a-32c, but may be made of any of
various ordinary electrically conductive materials.
[0063] The electrodes 40a, 40b of the counter mechanism operate as
follows:
[0064] A voltage is continuously applied between the electrodes
40a, 40b. When no semiconductor chip 26 is present on the
electrodes 40a, 40b, a capacitor with air serving as a dielectric
medium is connected between the electrodes 40a, 40b, and a voltage
V.sub.1 is detected between the conductors 42. When a semiconductor
chip 26 is fed to a position near the terminal wall 28, i.e., over
the electrodes 40a, 40b, as shown in FIG. 5, a capacitor with the
semiconductor chip 26 serving as a dielectric medium is connected
between the electrodes 40a, 40b, and a voltage V.sub.2 which is
lower than the voltage V.sub.1 is detected between the conductors
42. The voltage between the conductors 42 is continuously detected
by a circuit (not shown) of the counter mechanism to count the
number of times that the detected voltage varies, and the counter
number can be recognized as the number of semiconductor chips 26
that have been fed to the position near the terminal wall 28.
[0065] Since one at a time of semiconductor chips 26 is reliably
fed to the position near the terminal wall 28 by the stopper
mechanism, semiconductor chips 26 are prevented from unduly
overlapping each other or being joined to each other at position
near the terminal wall 28. Consequently, the number of fed
semiconductor chips 26 can reliably be counted by the counter
mechanism. Using the count information from the counter mechanism,
it is possible to control the rate at which semiconductor chips 26
are fed down the feed paths 12 for automatizing the article feeding
apparatus 10.
[0066] If the electrodes of the counter mechanism are be located at
an intermediate position in each of the feed paths 12, as described
above, then the counter mechanism may be used as a sensor for
detecting when a certain number of semiconductor chips 26 remain
stagnant between the unloading position at the terminal end of the
feed path 12 and the intermediate position.
[0067] Although certain preferred embodiments of the present
invention have been shown and described in detail, it should be
understood that various changes and modifications may be made
therein without departing from the scope of the appended
claims.
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