U.S. patent application number 11/039039 was filed with the patent office on 2006-07-20 for component carrier and method for making.
Invention is credited to James T. Adams, William J. Bryan, Daniel F. Cronch, Jose P. de Souza, Bryan C. Feisel, Carsten Franke, Brent R. Hansen, Mitchell T. Huang, Nelson D. Sewall, David F. Slama, Joseph E. Weiler.
Application Number | 20060157381 11/039039 |
Document ID | / |
Family ID | 36498811 |
Filed Date | 2006-07-20 |
United States Patent
Application |
20060157381 |
Kind Code |
A1 |
Adams; James T. ; et
al. |
July 20, 2006 |
Component carrier and method for making
Abstract
A carrier tape includes a longitudinal strip having a plurality
of component receiving pockets positioned therein. The pocket depth
is greater than a thickness of the longitudinal strip. Adjacent
pockets are spaced apart by a distance less than approximately five
times the thickness of the longitudinal strip. Sidewalls separating
adjacent pockets have a height greater than the pocket depth minus
a height of a component which the pockets are configured to
receive. The carrier tape is produced by providing a rotatable tool
and a nip roll having a conformable outer circumferential surface
opposed to the tool. The outer circumferential surface of the tool
includes projections for forming the pockets. A polymer web is
introduced into a nip between the tool and the nip roll, and
embossed with the projections on the circumferential surface of the
tool.
Inventors: |
Adams; James T.; (Austin,
TX) ; Bryan; William J.; (Mahtomedi, MN) ;
Cronch; Daniel F.; (Austin, TX) ; de Souza; Jose
P.; (Austin, TX) ; Feisel; Bryan C.; (Hudson,
WI) ; Franke; Carsten; (St. Paul, MN) ;
Hansen; Brent R.; (New Richmond, WI) ; Huang;
Mitchell T.; (Austin, TX) ; Sewall; Nelson D.;
(Forest Lake, MN) ; Slama; David F.; (Grant,
MN) ; Weiler; Joseph E.; (Hutchinson, MN) |
Correspondence
Address: |
3M INNOVATIVE PROPERTIES COMPANY
PO BOX 33427
ST. PAUL
MN
55133-3427
US
|
Family ID: |
36498811 |
Appl. No.: |
11/039039 |
Filed: |
January 20, 2005 |
Current U.S.
Class: |
206/713 |
Current CPC
Class: |
H05K 13/0084
20130101 |
Class at
Publication: |
206/713 |
International
Class: |
B65D 85/00 20060101
B65D085/00 |
Claims
1. A component carrier tape comprising: a longitudinal flexible
strip; a plurality of pockets longitudinally positioned on the
longitudinal strip and configured for receiving a component
therein, each of the pockets having a depth from a top surface of
the longitudinal strip that is greater than a thickness of the
longitudinal strip; wherein side walls separating adjacent pockets
are spaced apart by a distance less than approximately five times
the thickness of the longitudinal strip, and wherein the sidewalls
separating the adjacent pockets have a height greater than the
pocket depth minus a height of the component which the pockets are
configured to receive.
2. The component carrier tape of claim 1, wherein the longitudinal
strip has first and second parallel longitudinal edge surfaces, and
at least one of the edge surfaces includes a plurality of equally
spaced advancement holes for receiving an advancement
mechanism.
3. The component carrier tape of claim 1, further comprising a
cover releaseably secured to a top surface of the longitudinal
strip, extending along the strip, and covering the plurality of
pockets.
4. The component carrier tape of claim 1, wherein the longitudinal
strip has a width of less than 10 mm.
5. The component carrier tape of claim 1, wherein the plurality of
pockets are spaced on the longitudinal strip at a pitch of about 2
mm or less.
6. The component carrier tape of claim 1, wherein side walls
separating adjacent pockets are spaced apart by a distance less
than approximately three times the thickness of the longitudinal
strip.
7. The component carrier tape of claim 1, wherein the sidewalls
separating adjacent pockets have a height greater than
approximately 90% of the pocket depth.
8. The component carrier tape of claim 1, wherein the sidewalls
separating adjacent pockets have a height greater than
approximately 95% of the pocket depth.
9. The component carrier tape of claim 1, wherein the sidewalls
separating the adjacent pockets have a height approximately equal
to the pocket depth.
10. The component carrier tape of claim 1, wherein the pockets have
a length and a width, and wherein at least one of the pocket length
and pocket width is less than 2 mm.
11. The component carrier tape of claim 10, wherein the pockets
have a length and a width, and wherein at least one of the pocket
length and pocket width is less than 1 mm.
12. The component carrier tape of claim 1, wherein the longitudinal
strip has a thickness of less than about 0.5 mm.
13. The component carrier tape of claim 12, wherein the
longitudinal strip has a thickness of less than about 0.25 mm.
14. A flexible carrier tape for storage and delivery of components
by an advancement mechanism, the carrier tape comprising: a
longitudinal flexible strip having a top surface and a bottom
surface opposite the top surface; a plurality of pockets for
receiving components spaced along the strip and opening through the
top surface thereof, wherein adjacent pockets are separated from
each other by a crossbar, the crossbar separating adjacent recesses
by a distance less than approximately three times a thickness of
the strip, and wherein a top surface of the crossbar is
substantially coplanar with the top surface of the strip; and a
plurality of projections extending from the bottom surface of the
strip, each one of the projections corresponding to one of the
plurality of pockets.
15. A method for producing an embossed carrier tape having a
plurality of longitudinally spaced component receiving pockets in a
front side thereof, comprising: providing a rotatable tool having
an outer circumferential surface, the outer circumferential surface
including a series of projections for forming a plurality of
longitudinally spaced component receiving pockets; providing a nip
roll having a conformable outer circumferential surface opposed to
the outer circumferential surface of the tool; introducing a
polymer web into a nip between the tool and the nip roll; pressing
the polymer web between the tool and the nip roll to emboss the web
with the projections on the circumferential surface of the tool;
and removing the embossed web from the tool.
16. The method of claim 15, wherein providing a rotatable tool
having an outer circumferential surface including a series of
projections comprises providing projections having a height greater
than a thickness of embossed web removed from the tool.
17. The method of claim 15, wherein providing a rotatable tool
having an outer circumferential surface including a series of
projections comprises providing projections separated by a distance
less than about five times the thickness of the embossed web
removed from the tool.
18. The method of claim 17 wherein providing a rotatable tool
having an outer circumferential surface including a series of
projections comprises providing projections separated by a distance
less than about three times the thickness of the embossed web
removed from the tool.
19. The method of claim 15, wherein providing a rotatable tool
having an outer circumferential surface including a series of
projections comprises providing projections to form a plurality of
individual carrier tapes in the embossed web.
20. The method of claim 15, wherein providing a nip roll having a
conformable outer circumferential surface comprises providing a
conformable circumferential surface having a Shore A hardness in
the range of 30 to 100.
21. The method of claim 15, wherein providing a nip roll having a
conformable outer circumferential surface comprises covering a
circumferential surface of the nip roll covered with an
elastomer.
22. The method of claim 15, wherein pressing the polymer web
between the tool and the nip roll includes deforming the
conformable surface of the nip roll with the projections of the
rotatable tool to form features on a back side of the web.
23. The method of claim 15, wherein providing a rotatable tool
comprises providing a unitary tool.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to carrier tapes of
the kind having a plurality of pockets spaced longitudinally on the
tape for accommodating components therein. More particularly, the
invention relates to carrier tapes for very small components, and a
method for producing such carrier tapes.
BACKGROUND
[0002] In general, carrier tapes that are used to hold and
transport components are well known. For example, in the field of
electronics circuit assembly, electronic components are often
carried from a supply of components to a specific location on a
circuit board for attachment thereto. The components may be of
several different types, including surface mount components.
Particular examples include memory chips, integrated circuit chips,
resistors, connectors, processors, capacitors, gate arrays,
etc.
[0003] Rather than manually affixing each individual electronic
component to a circuit board, the electronics industry makes
extensive use of robotic placement machines, sometimes known as
"pick-and-place" machines, that grasp a component at a specific
location (i.e., from the carrier tape) and place it at another
specific location (i.e., on a printed circuit board). Grasping of
the components is commonly accomplished with a vacuum pick-up
device that grasps the top of the component by suction. Robotic
placement equipment is typically programmed to repeat a precise
sequence of movements in every cycle. For electronic component
assembly, the robotic equipment may be programmed to grasp a memory
chip, for example, and place it in a specific location on a circuit
board. To ensure the sustained operation of the robotic placement
machine, a continuous supply of electronic components must be
furnished to the machine at a predetermined rate and location. It
is therefore important that each component be located in the same
position (i.e., the point at which the robotic placement machine
grasps the component) as each preceding and succeeding
component.
[0004] A common way to provide a continuous supply of electronic
components to robotic placement equipment is to use a carrier tape.
Conventional carrier tapes generally comprise an elongated strip
that has a series of identical pockets formed at predetermined,
uniformly spaced intervals along the length of the tape. The
pockets are each designed to receive an electronic component
therein. Frequently, the pockets are sized to match a particular
component. The component manufacturer typically loads components
into the series of pockets. After components are placed in the
pockets, a cover tape is applied over the elongated strip to retain
the components in their respective pockets. The loaded carrier tape
is wound into a roll or onto a reel, and then transported from the
component manufacturer to another manufacturer or assembler, where
the roll of carrier tape may be mounted within some type of
assembly equipment. The carrier tape is typically unwound from the
roll and automatically advanced toward a robotic pick-up location.
Advancement of the carrier tape is commonly accomplished using a
series of through-holes uniformly spaced along one or both edges of
the elongated strip forming the carrier tape. The through-holes
receive the teeth of a drive sprocket that advances the tape toward
the robotic placement machine. Eventually, the cover tape is
stripped from the carrier tape, the components are removed from the
pockets and then placed onto the circuit board.
[0005] It is known to form carrier tapes using a rotating drum. The
rotating drum has a plurality of molds disposed around its
circumference. The molds may be convex (i.e., male) or concave
(i.e., female) molds, and are sized to provide the desired final
pocket dimensions, accounting for the thickness of the tape, the
depth of the pocket, and the thermal contraction of the tape after
molding. An exemplary method for producing carrier tape using a
convex rotary mold is described in U.S. Pat. No. 5,800,772 to
Kurasawa. In the production of an embossed carrier tape using a
convex rotary mold, a web of material is incrementally heated to
its softening temperature, and is then guided to pass around the
periphery of the drum. The softened material drapes over the molds
and comes into close contact with generally the entire side
surfaces of the convex molds except for those portions of the web
located between adjacent convex molds. At the same time, the web is
vacuum-drawn against the molds to urge the web into the spaces
between adjacent molds.
[0006] Rotary molds used in vacuum forming as described above are
generally constructed by stacking a plurality of drum sections as
described in U.S. Pat. No. 5,800,772. When a plurality of drum
sections are assembled together, a forming tool is created. The
space between the drum sections enables the use of vacuum to draw
down a molten web to form pocket features.
[0007] The ongoing trend in electronics towards smaller and smaller
products requires continued miniaturization of electronic
components. Needs exist for packaging small electronic components
on the order of 1 millimeter (0.040 inches) length by 0.5
millimeter (0.020 inches) width and smaller. One of the major
challenges in producing carrier tapes for small components is to
consistently meet increasingly fine dimensional accuracy and
precision requirements. The current methods used to make forming
tools have significant drawbacks for producing carrier tape to
package small components. For example, when vacuum forming using a
rotating drum it becomes increasingly difficult to draw the web
into and between the smaller and more closely spaced molds.
Consequently, it is more difficult to keep carrier tape feature
dimensions within required tolerances, and features of the carrier
tape are not always fully and accurately formed. When the
dimensions of carrier tape features approach the same order of
magnitude as the thickness of the web, forming the carrier tape
with the necessary precision becomes increasingly problematic.
[0008] For producing very small features in a polymer sheet, it is
known to emboss a polymer web of material between a mold tool and a
nip roll formed of steel or chrome. The thickness of the web
exceeds the height of features on the tool, such that features are
formed on the side of the web in contact with the tool features,
and the backside of the web (in contact with the nip roll) is
completely flat and featureless. Such a construction applied to a
carrier tape would not only use more polymer (leading to greater
costs), but the dimensions and reduced flexibility of the thick
tape would also adversely affect compatibility with many automated
systems.
[0009] If carrier dimensions are not kept within fine tolerances
and features of the carrier tape are not fully and accurately
formed, components could be caught in the pockets, be wobbly or
unstable in the pockets, migrate to an incorrect position, or turn
over completely. Since it is virtually impossible to correct the
attitude of a component in a pocket, a part improperly positioned
in a pocket can fail to be picked out of the pocket or can be
improperly picked as it is removed from the pocket. As a
consequence, an improperly positioned part may not be successfully
mounted on a printed circuit board or the like.
SUMMARY
[0010] In one aspect, the invention described herein provides a
component carrier tape. In one embodiment according to the
invention, the component carrier tape comprises a longitudinal
flexible strip having a plurality of pockets longitudinally
positioned on the longitudinal strip. The pockets are configured
for receiving a component therein. Each of the pockets has a depth
from a top surface of the longitudinal strip that is greater than a
thickness of the longitudinal strip. The side walls separating
adjacent pockets are spaced apart by a distance less than
approximately five times the thickness of the longitudinal strip,
and the sidewalls separating the adjacent pockets have a height
greater than the pocket depth minus a height of the component which
the pockets are configured to receive.
[0011] In another embodiment according to the invention, the
carrier tape comprises a longitudinal flexible strip having a top
surface and a bottom surface opposite the top surface. A plurality
of pockets for receiving components are spaced along the strip and
open through the top surface of the strip. Adjacent pockets are
separated from each other by a crossbar. The crossbar separates
adjacent recesses by a distance less than approximately three times
a thickness of the strip, and a top surface of the crossbar is
substantially coplanar with the top surface of the strip. A
plurality of projections extend from the bottom surface of the
strip, each one of the projections corresponding to one of the
plurality of pockets.
[0012] In another aspect, the invention described herein provides a
method for making a component carrier tape. In one embodiment
according to the invention, the method comprises providing a
rotatable tool having an outer circumferential surface and a nip
roll having a conformable outer circumferential surface opposed to
the outer circumferential surface of the tool. The outer
circumferential surface of the rotatable tool includes a series of
projections for forming a plurality of longitudinally spaced
component receiving pockets. A polymer web is introduced into a nip
between the tool and the nip roll, and the polymer web is pressed
between the tool and the nip roll to emboss the web with the
projections on the circumferential surface of the tool. The
embossed web is then removed from the tool.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a fragmentary perspective view of one embodiment
of a carrier tape according to the invention, with an optional
cover thereof having been partially removed to show components
stored within pockets of the carrier tape. The component has been
omitted from the leading pocket to show the interior of the pocket
more clearly.
[0014] FIG. 2 is a sectional view taken along line 2-2 in FIG.
1.
[0015] FIG. 3 is a schematic illustration of an exemplary process
according to the invention for producing the carrier tape of FIGS.
1 and 2.
[0016] FIG. 4 is a photograph of a carrier tape produced using
prior art processes, showing incompletely formed crossbar features
separating adjacent pockets.
[0017] FIG. 5 is a photograph of a carrier tape produced using
processes according to the invention, showing completely formed
crossbar features separating adjacent pockets.
DETAILED DESCRIPTION
[0018] In the following detailed description of the preferred
embodiments, reference is made to the accompanying drawings, which
form a part hereof, and in which is shown by way of illustration
specific embodiments in which the invention may be practiced. It is
to be understood that other embodiments may be utilized and
structural or logical changes may be made without departing from
the scope of the present invention. The following detailed
description, therefore, is not to be taken in a limiting sense, and
the scope of the present invention is defined by the appended
claims.
[0019] The present invention provides a component holding or
transport device having a plurality of pockets formed therein that
can be used in the storage or transport of a variety of types of
components. More particularly, the present invention provides a
holding or transport device having very small precisely formed
pockets for use with very small components. In one implementation,
the present invention provides a longitudinal component carrier
tape having a plurality of closely spaced pockets for storing,
transporting, and otherwise handling electronic or other
components. Although illustrative embodiments of component carries
are described below with reference to carrier tapes for use with
electronic components, it is understood that the component carriers
may be adapted for use with materials or substances of any type.
For example, the features and materials of the component carriers
may be adapted for use with liquid sample materials (or sample
materials entrained in a liquid), as may be used in sample
processing devices like those described in U.S. patent application
Ser. No. 10/682,597, filed Oct. 9, 2003.
[0020] Referring now to the drawings, one embodiment of a carrier
tape according to the invention is shown in FIGS. 1 and 2. The
illustrated carrier tape is particularly useful for the storage and
delivery of small electronic components by an advancement
mechanism. For purposes of the invention, small components are
those having at least one dimension on the order of 1 millimeter
(0.040 inches) and smaller.
[0021] A unitary flexible carrier tape 100 has a strip portion 101
defining a top surface 102 and a bottom surface 103 opposite the
top surface 102. Strip portion 101 includes longitudinal edge
surfaces 104 and 106, and a row of aligned advancement holes 108
and 110 formed in and extending along one, and preferably both,
edge surfaces. Advancement holes 108 and 110 provide a means for
receiving an advancement mechanism such as the teeth of a sprocket
drive (not shown) for advancing carrier tape 100 toward a
predetermined location.
[0022] A series of pockets 112 is formed in and spaced along strip
portion 101, the pockets opening through the top surface 102 of the
strip portion. Within a given carrier tape, each pocket 112 is
usually practically identical to the other pockets. Typically, the
pockets 112 are aligned with each other and equally spaced apart.
In the illustrated embodiment, each pocket 112 includes four side
walls 114, each at generally right angles with respect to each
adjacent wall. Side walls 114 adjoin and extend downwardly from the
top surface 102 of the strip portion and adjoin bottom wall 116 to
form pocket 112. Bottom wall 116 is generally planar and parallel
to the plane of strip portion 101. The transverse side walls 114 of
adjacent longitudinally positioned pockets 112 define crossbars 117
that separate adjacent pockets 112.
[0023] Pockets 112 may be designed to conform to the size and shape
of the components that they are intended to receive. Alternately,
pocket 112 may have a generic design to readily accommodate
components of varying sizes and/or shapes. Although not
specifically illustrated, the pockets may have more or less side
walls than the four that are shown in the preferred embodiment. In
general, each pocket includes at least one side wall 114 that
adjoins and extends downwardly from strip portion 101, and a bottom
wall 116 that adjoins the side wall 114 to form the pocket 112.
Thus, the pockets 112 may be circular, oval, triangular,
pentagonal, or have other shapes in outline. Each side wall 114 may
also be formed with a slight draft (i.e., a slant toward the center
of the pocket) to facilitate insertion of the component, and to
assist in releasing the pocket from a mold or forming die during
fabrication of the carrier tape. The depth of the pocket can also
vary depending on the component that the pocket is intended to
receive. In addition, the interior of the pockets 112 may be formed
with ledges, ribs, pedestals, bars, rails, appurtenances, and other
similar structural features to better accommodate or support
particular components.
[0024] Although a single column of pockets 112 is illustrated in
the drawings, two or more columns of aligned pockets could also be
formed along the length of the strip portion 101 to facilitate the
simultaneous delivery of multiple components. The columns of
pockets could be arranged parallel to each other with pockets in
one column being in aligned rows with the pockets in the adjacent
column(s), as described in U.S. Pat. No. 4,298,120. Alternately,
the pockets in adjacent columns may be offset from each other, as
described in U.S. Pat. No. 4,724,958.
[0025] In component carriers according to the invention, the side
walls 114 of adjacent pockets 112 are separated by a distance less
than about five (5) times the web thickness, preferably less than
about three (3) times the web thickness; and the top edges of the
walls 114 separating adjacent pockets 112 are substantially
coplanar with the top surface 102 of strip portion 101. The height
of the adjacent side walls 114 is greater than the pocket depth
minus the component height, to prevent component migration between
adjacent pockets. In some embodiments, the height of the adjacent
side walls is approximately 90% of the pocket depth or greater,
preferably approximately 95% of the pocket depth or greater, and
more preferably equal to the pocket 112 depth. In some embodiments,
the depth of the pockets 112 is greater than the thickness of the
web forming strip portion 101, while in other embodiments the depth
of the pockets 112 is less than the thickness of the web forming
strip portion 101. In either case, the pockets 112 produce
corresponding projections on the bottom surface of strip portion
101. In some embodiments, at least one of a length of the pocket
and a width of the pocket is less than 2 mm, preferably less than 1
mm. In other embodiments, the strip portion has a width of less
than approximately 16 mm for multi-row embodiments, and less than
approximately 10 mm for single row embodiments. In still other
embodiments, the plurality of pockets 112 are spaced along the
longitudinal strip at a pitch of approximately 2 mm or less.
[0026] The web forming strip portion 101 may have any thickness, so
long as the web has sufficient flexibility to permit it to be wound
about the hub of a storage reel. In some embodiments according to
the invention, strip portion has a thickness of less than about 1
mm (40 mil), preferably less than about 0.5 mm (20 mil). In some
embodiments, the strip portion has a thickness less than about 0.25
mm (10 mil). Strip portion 101 may be optically clear, pigmented or
modified to be electrically dissipative or conductive. The
electrically conductive material allows an electric charge to
dissipate throughout the carrier tape and preferably to the ground.
This feature may prevent damage to components contained within the
carrier tape due to an accumulated static electric charge.
[0027] Carrier tape 100 may optionally include an elongate cover
tape 120. Cover tape 120 is applied over the pockets 112 of the
carrier tape 100 to retain the components therein. An exemplary
component 118 is schematically illustrated in FIGS. 1 and 2. Cover
tape 120 can also protect the components from dirt and other
contaminants that could invade the pockets. As best shown in FIGS.
1 and 2, cover tape 120 is flexible, overlies part or all of
pockets 112, and is disposed between the rows of advancement holes
108 and 110 along the length of strip portion 101. Cover tape 120
is releasably secured to the top surface of strip portion 101 so
that it can be subsequently removed to access the stored
components. As illustrated, cover tape 120 includes parallel
longitudinal bonding portions 122 and 124 that are bonded to
longitudinal edge surfaces 104 and 106, respectively, of strip
portion 101. For example, a pressure sensitive adhesive such as an
acrylate material, or a heat-activated adhesive such as an ethylene
vinyl acetate copolymer, may be used to adhere the cover to edge
surfaces 104 and 106. Alternatively, cover tape 120 could be
secured to strip portion 101 by other means. Cover tape 120 could
also be omitted, and components retained in the pockets 112 by an
adhesive, for example.
[0028] In one exemplary embodiment, the carrier tapes according to
the present invention are made by shaping the pockets 112 in a
sheet of polymeric material and winding the carrier tape onto a
reel to form a roll. FIG. 3 schematically shows an apparatus and
manufacturing process used in the production of a component carrier
tape according to the present invention. A rotatable tool 200 has a
structured outer circumferential surface 202. The surface 202
includes projections 204 extending therefrom that correspond to the
various features to be formed in a component carrier tape 100,
e.g., component pockets 112, alignment features within the pockets,
bosses for sprocket or alignment holes, etc. For purposes of
illustration, projections 204 have been greatly enlarged in the
schematic representation of FIG. 3.
[0029] A nip roll 210 having a conformable outer circumferential
surface 212 is in contact with and opposes the outer
circumferential surface 202 of the rotatable tool 200, such that
the projections 204 press into and deform the surface 212 of the
nip roll 210. The circumferential surface 212 of the nip roll 210
is preferably covered with an elastomeric material. Suitable
elastomeric materials include, but are not limited to, rubbers,
silicones, ethylene propylene diene monomers (EPDM), urethanes,
Teflon.RTM., nitrites, neoprenes, and fluoroelastomers. In some
embodiments, the conformable outer surface 212 of the nip roll 210
has a Shore A hardness in the range of 30 to 100, preferably in the
range of 50 to 90, depending upon the material being formed.
[0030] A melt-processable polymer is delivered from an extruder 220
to a slot die apparatus 222. The melt-processable polymer is
delivered to the slot die apparatus 222 at or above its melting
temperature (i.e., the temperature at which it can be formed or
molded). A web 230 of polymer is discharged from the die apparatus
222 into the nip 240 between the rotatable tool 200 and the nip
roll 210. In some implementations, it may be preferred that the
polymer web 230 be drop cast onto the rotatable tool 200 just
before the nip 240 formed with the nip roll 210. The conformable
outer surface 212 of the nip roll 210 deforms as the polymer web
230 is pressed between the rotatable tool 200 and the nip roll 210
and embossed with the features of the rotatable tool 200. The
pressure applied to the web 230 by the conformable nip roll 210 is
sufficient to force molten resin of web 230 into small crevices
between projections 204 (forming features of the carrier tape 100
such as narrow pocket crossbars 117) of the rotatable tool 200, and
to provided backside feature definition to the web 230 (i.e.,
features are defined on bottom surface 103 of strip portion 101).
The pressure applied by the conformable nip roll 210 will depend
upon a plurality of factors, including process speed, material
viscosity, web thickness, and dimensions and spacing of projections
204 on rotatable tool 200.
[0031] The dimensions of the incoming polymeric web 230 will be
determined by the gauge and width of the carrier tape 100 that is
to be formed. It is preferred that the thickness of the polymer web
230 and the pressure between the rotatable tool 200 and the nip
roll 210 be controlled such that the thickness of the web 230
exiting the nip 240 is less than the height of the projections 204
that form the component pockets 112 of the carrier tape 100. In a
preferred embodiment, the polymer web 230 is delivered to the nip
240 at a thickness in the range of 5 mils to 20 mils.
[0032] In some implementations, it may be preferred that the
polymer web 230 be delivered from the die apparatus 222 to the
rotatable tool 200 at a temperature that is at or above its melt
processing temperature. By providing the polymer web 230 to the
rotatable tool 200 at or above its melt processing temperature, the
polymer can adequately form or be replicated to the shape of the
projections 204 on the rotatable tool 200. The temperature at which
the polymeric web 230 must be delivered from the die apparatus 222
varies over a broad range (i.e., about 200.degree. to over
630.degree. F.) depending upon the gauge and type of material that
is being formed, as well as the speed of the manufacturing line.
Although the tool 200 is depicted and described herein as a roll,
it should be understood that the tool 200 may alternatively be
provided as any other rotatable structure amenable to continuous
web-form processing, such as a continuous belt.
[0033] The temperature of the polymer web is preferably lowered to
below the melt processing temperature at some point after the nip
240 between the rotatable tool 200 and the nip roll 210 to retain
the structures formed in the polymer web 230 and provide mechanical
stability to the web. To aid in temperature control of the web 230,
the rotatable tool 200 and/or the nip roll 210 may be heated or
cooled, as necessary. The result of the processing depicted in FIG.
3 is an embossed web 250 that can be used to form the carrier tapes
100 according to the present invention.
[0034] In the case of extrusion of thermoplastic resins, a web of
molten material is guided to pass through the nip 240. As the
embossed web 250 exits the nip 240, any suitable cooling means may
be employed to cool the web and sufficiently harden the material
such that it may be removed from the rotatable tool 200. Cooling
can be accomplished, for example, by convective air cooling, direct
impingement of air jets by high-pressure blowers, a water bath or
spray, or a cooling oven until the thermoplastic polymer
sufficiently solidifies.
[0035] In the case of polymerizable resins, the resin may be poured
or pumped directly into a dispenser that feeds the slot die
apparatus 222. For embodiments wherein the polymer resin is a
reactive resin, the method of manufacturing the web further
comprises curing the resin in one or more steps. For example, the
resin may be cured upon exposure to a suitable radiant energy
source such a actinic radiation, ultraviolet light, visible light,
etc., depending upon the nature of the polymerizable resin to
sufficiently harden the resin prior to removal from the rotatable
tool 200. Combinations of cooling and curing may also be employed
in hardening the web as it comes off the tool 200.
[0036] Suitable resin compositions for component carrier tapes of
this invention are dimensionally stable, durable, and readily
formable into the desired configuration. Suitable materials
include, but are not limited to, polyesters (e.g., glycol-modified
polyethylene terephthalate, or polybutylene terephthalate),
polycarbonate, polypropylene, polystyrene, polyvinyl chloride,
acrylonitrile-butadiene-styrene, amorphous polyethylene
terephthalate, polyamide, polyolefins (e.g. polyethylene,
polybutene, or polyisobutene), modified poly (phenylene ether),
polyurethane, polydimethylsiloxane, acrylonitrile-
butadiene-styrene resins, and polyolefin copolymers. In some
embodiments, the material has a melt temperature in the range of
400.degree. to 630.degree. F. The material may be modified to be
electrically dissipative or conductive. In the latter case, the
material may include an electrically conductive material, such as
carbon black or vanadium pentoxide, that is either interspersed
within the polymeric material or is subsequently coated onto the
web. These materials may also include dyes, colorants, pigments, UV
stabilizers, or other additives.
[0037] In general, the rotatable tool 200 may be comprised of any
substrate suitable for forming by direct machining. Suitable
substrates machine cleanly with minimal or no burr formation,
exhibit low ductility and low graininess, and maintain dimensional
accuracy after machining. A variety of machinable metals or
plastics may be utilized. Suitable metals include aluminum, steel,
brass, copper electroless nickel, and alloys thereof. Suitable
plastics comprise thermoplastic or thermoset materials such as
acrylics or other materials. In some embodiments, the material
forming rotatable tool 200 may comprise a porous material, such
that a vacuum can be applied through the material of rotatable tool
200, in combination with nip roll 210.
[0038] The rotatable tool 200 is preferably formed as a unitary
sleeve having projections 204 for all of the desired carrier tape
100 features on the unitary sleeve. The sleeve may include
projections for forming the pockets, alignment features thereof,
and protuberances for skiving to form sprocket holes, for example.
The method includes simultaneously thermoforming the pockets and
the protuberances to provide excellent registration
therebetween.
[0039] Projections on the outer circumference 202 of the rotatable
tool 200 are preferably cut directly onto the sleeve using either a
carbide or diamond tooling machine that is capable of shaping each
projection with fine precision. Moore Special Tool Company,
Bridgeport, Conn.; Precitech, Keen, N.H.; and Aerotech Inc.,
Pittsburgh Pa., manufacture suitable machines for such purposes.
Such machines typically include a laser interferometer-positioning
device, a suitable example of which is available from Zygo
Corporation, Middlefield Conn. The diamond tools suitable for use
are those such as can be purchased from K&Y Diamond, Mooers,
N.Y., or Chardon Tool, Chardon, Ohio.
[0040] The sleeve can be machined using techniques and methods
known in the art to form the desired projections 204 thereon. For
example, the projection surfaces corresponding to the component
pocket sidewalls 114 can be formed by turning the sleeve in a
typical lathe operation in which the sleeve is turned and the
cutter is in a fixed position. The projection surfaces
corresponding to the component pocket crossbars 117 can be formed
by holding the sleeve stationary and cutting slots parallel to the
axis of the sleeve. Addition projections, such as those for forming
posts for skiving, can be formed in a manner similar to the
formation of the projections used to shape the pockets.
Beneficially, projections 204 on the sleeve can be formed to
simultaneously produce a plurality of carrier tapes. Specifically,
pockets and other features for a plurality of carrier tapes can be
produced on a single sleeve, and the web 250 slit after forming to
isolate the individual carrier tapes.
[0041] Once the pockets 112 of the carrier tape 100 have been
prepared, the advancement holes 108, 110 are subsequently formed in
a separate operation such as by punching the strip portion 101, or
by skiving off protuberances formed on one or both of longitudinal
edge surfaces 104 and 106 as described, for example, in U.S. Pat.
No. 5,738,816. The carrier tape 100 is then wound (either
concentric or level windings) about a reel 260 to form a supply
roll for storage until the carrier tape is loaded with
components.
[0042] FIG. 4 is a photograph of a typical vacuum formed carrier
tape formed on male-featured tooling using a conductive black
polycarbonate resin. The low pocket crossbars result from the
restricted flow of resin into the narrow crevices between the
pockets in the tooling.
[0043] FIG. 5 is a photograph of a carrier tape formed using a
static dissipative black polystyrene resin in an extrusion
replication process with a conformable nip roll 210 according to
the invention. The crossbars of the carrier are fully formed.
Clearly, the production method and apparatus of the present
invention produces significantly higher pocket crossbars than the
standard vacuum formed pocket crossbars.
[0044] In experimental results, where a fully formed crossbar has a
height of 0.631 mm, average crossbar heights obtained using
conductive black polycarbonate in a standard vacuum forming process
pockets were 0.107 mm, while average crossbar heights obtained
using identical material in the extrusion replication process of
the invention were 0.607 mm. Thus, a standard vacuum forming
process produced a crossbar height equal to approximately 17%
(0.107 mm/0.631 mm) of a fully formed crossbar height, while the
extrusion replication process of the invention produced a crossbar
height equal to approximately 96% (0.607 mm/0.631 mm) of a fully
formed crossbar height.
Process Example
[0045] A component carrier tape according to the invention was
prepared using a static dissipative polystyrene resin filled with
carbon black. The resin was fed into a single screw 2.5-inch Davis
Standard extruder with a length/diameter (L/D) ratio of 30:1. A
rising temperature profile was used in the extruder die zones,
reaching a final temperature of 450.degree. F. The molten polymer
was passed through a heated neck tube into a 10-inch wide film die
block shimmed to a nominal gap of 0.070 inches. The web melt
emerging from the extruder die block was drop cast into a nip
formed by an aluminum forming tool and a silicone rubber covered
nip roll. The silicone rubber had a Shore A hardness of 75. The
tool roll temperature was maintained at 100.degree. F., while the
nip roll temperature was maintained at 70.degree. F. After exiting
the nip, the web continued around the curved surface of the tool as
it was cooled by contact with a chilled forming tool, and also by
external compressed air cooling until a temperature of less than
the glass transition temperature of the material (approximately
212.degree. F.) was reached. The web was then removed from the tool
and wound into a roll.
[0046] Although specific embodiments have been illustrated and
described herein for purposes of description of the preferred
embodiment, it will be appreciated by those of ordinary skill in
the art that a wide variety of alternate and/or equivalent
implementations calculated to achieve the same purposes may be
substituted for the specific embodiments shown and described
without departing from the scope of the present invention. Those
with skill in the art will readily appreciate that the present
invention may be implemented in a very wide variety of embodiments.
This application is intended to cover any adaptations or variations
of the preferred embodiments discussed herein. Therefore, it is
manifestly intended that this invention be limited only by the
claims and the equivalents thereof.
* * * * *