US20080087572A1

US20080087572A1 - Component carrier and method for making

Info

Publication number: US20080087572A1
Application number: US11/867,088
Authority: US
Inventors: Charlie V. Wihren
Original assignee: 3M Innovative Properties Co
Current assignee: 3M Innovative Properties Co
Priority date: 2006-10-17
Filing date: 2007-10-04
Publication date: 2008-04-17
Also published as: KR20090071595A; JP2010507257A; DE112007002445T5; TW200833570A; CN101528565A; WO2008048785A1

Abstract

A component carrier tape having 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 separated from an adjacent pocket by a crossbar; wherein at least one crossbar includes at least one release feature.

Description

REFERENCE TO CROSS-RELATED APPLICATIONS

The present application claims priority to U.S. Provisional Patent Application 60/829,807, filed Oct. 17, 2006.

FIELD

The present invention relates generally to carrier tapes having a plurality of pockets spaced longitudinally on the tape for accommodating components therein.

BACKGROUND

In general, carrier tapes that are used to hold and transport components are well known. For example, in the field of electronics circuit assembly, 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, which pockets are each designed to receive an electronic component therein. 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.

SUMMARY

Carrier tapes may be formed 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. In the production of an embossed carrier tape using a convex rotary mold, typically a web of pliable material is guided 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. The web may be vacuum-drawn against the molds, or pressed against the molds by a nip roll, to urge the web into the spaces between adjacent molds. After the pliable web material takes on the shape of the molds, cooling and hardening of the web material is initiated and the shaped web material is removed from the molds. Because the shaped web material has not completely hardened at the time it is removed from the molds, uneven stresses applied to portions of the shaped web material can cause desired features of the resulting carrier tape to be skewed or misshapen.
At least one aspect of the present invention provides 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 separated from an adjacent pocket by a crossbar; wherein at least one crossbar includes at least one release feature. The component carrier tape may have multiple release features on a single crossbar. The multiple release features may differ with respect to one or more of size, shape, height, width, depth, and spacing. The uppermost portion of the release feature may be at or below the plane of the longitudinal flexible strip. A release feature may be a trough. There may be more than one trough and the troughs may be separated by a ridge. Alternatively, two ridges may be separated by a trough. The release feature may act as a hinge as the component carrier tape is removed from a forming tool. In some embodiments, the release feature may flex at an angle of up to about 45 degrees.
Another aspect of the present invention provides 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; and wherein a top surface of at least one the crossbar has at least one release feature.
Yet another aspect of the present invention provides a method for producing an embossed carrier tape 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 and at least one patterned depression between adjacent projections for forming at least one crossbar having at least one release feature between adjacent component receiving pockets; introducing a polymer web onto the tool; conforming the polymer web against the tool to emboss the web with the projections and depressions on the circumferential surface of the tool; and removing the embossed web from the tool.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a fragmentary perspective view of a carrier tape according to one embodiment of the invention.

FIG. 1B is a fragmentary perspective view of a carrier tape according to a second embodiment of the invention.

FIG. 1C is a cross-sectional view of the embodiment of FIG. 1B.

FIG. 2 is a schematic illustration of an exemplary process for producing a carrier tape according to an embodiment of the invention.

FIG. 3 is a photograph of a carrier tape according to one embodiment of the invention.

FIG. 4 is a photograph of a cross-section of a carrier tape according to one embodiment of the invention.

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.

DETAILED DESCRIPTION

At least one aspect of the present invention provides a longitudinal component carrier tape having a plurality of pockets for storing, transporting, and otherwise handling electronic or other components separated by crossbars on which are located one or more release features. Although illustrative embodiments of component carriers 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.
Referring now to the drawings, one embodiment of a carrier tape according to the invention is shown in FIG. 1A. 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.
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 sidewalls 114, each at generally right angles with respect to each adjacent wall. Sidewalls 114 adjoin and extend downwardly from the top surface 102 of the strip portion and adjoin bottom wall 116 to form pocket 112. Although not specifically illustrated, the pockets may have more or less sidewalls than the four that are shown in the preferred embodiment. The pockets 112 may be circular, oval, triangular, pentagonal, or have other shapes in outline. Bottom wall 116 is generally planar and parallel to the plane of strip portion 101. The transverse sidewalls 114 of adjacent longitudinally positioned pockets 112 define crossbars 117 that separate adjacent pockets 112. Crossbars 117 include release features 119. Release features 119 are two ridges separated by a trough. FIGS. 1B and 1C illustrate an alternate embodiment in which release features 119 are two troughs. The uppermost portions of the troughs are at or below the plane of strip portion 101.
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 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. Strip portion 101 may be optically clear, pigmented or modified to be electrically dissipative or conductive. 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.
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 FIG. 1A. Cover tape 120 can also protect the components from dirt and other contaminants that could invade the pockets. As best shown in FIG. 1A, 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.
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. 2 schematically shows an apparatus and manufacturing process used in the production of a component carrier tape according to one embodiment of the present invention. A rotatable tool 200 has a structured outer circumferential surface 202. The surface 202 includes projections 204 extending therefrom and depressions (not shown) that correspond to the various features to be formed in a component carrier tape 100, e.g., component pockets 112, crossbars 117, release features 119, 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. 2.
In the process illustrated in FIG. 2, 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 or 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 is embossed with the features of the rotatable tool 200. 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, 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. 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 pocket crossbars 117 and release features 119) 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).
As an alternative to using a nip roll, the web may be vacuum-drawn against the molds to urge the web into the spaces between adjacent molds. Rotary molds used in vacuum forming a carrier tape 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 suitable rotatable tool is created. The space between the drum sections enables the use of vacuum to draw down the web to form pocket features.
Additionally, as an alternative to extruding a melt-processable polymer onto the die apparatus, a pre-formed polymer sheet, which has been heated and softened, may be placed onto the rotatable tool. The pre-formed polymer sheet may be in the form of a continuous roll that is incrementally heated and fed onto the rotatable tool.
The temperature of the polymer web is preferably lowered to below the melt processing temperature at some point after it conforms to the shape of the rotatable tool 200 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, if used, may be heated or cooled, as necessary. The result of the processing depicted in FIG. 2 is an embossed web 250 that can be used to form the carrier tapes 100 according to the present invention.
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.
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° to 630° 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.
Although the tool 200 is depicted and described herein as a roll, the tool 200 may alternatively be provided as any other rotatable structure amenable to continuous web-form processing, such as a continuous belt. 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, or instead of, nip roll 210.
The rotatable tool 200 is preferably formed as a unitary sleeve having projections 204 and optionally depressions (not shown) for all of the desired carrier tape 100 features on the unitary sleeve. The sleeve may include projections for forming the pockets, alignment features, release features, and protuberances for skiving to form sprocket holes, for example. The sleeve may also include depressions for forming cross bars and release features. Whether a release feature is formed using a projection or depression will depend on the desired attributes of the release feature.
Projections and depression 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.
The sleeve can be machined using techniques and methods known in the art to form the desired projections 204 and depressions thereon. For example, the projection surfaces corresponding to the component pockets 112 and release features illustrated in FIGS. 1B and 1C 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 depressed surfaces corresponding to the component pocket crossbars 117 and release features 119 illustrated in FIG. 1A can be formed by holding the sleeve stationary and cutting slots or other features in the sleeve. Additional 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.
When the formed carrier tape 120 is removed from the rotatable tool 200, it can be difficult to separate the web material from the rotatable tool 200. Release features 119 on crossbars 117 aid in the release of the web material from the rotatable tool. The release features 119 contribute to a reduction in stress placed on the shaped web material when it is removed from the rotatable tool. Preferably, the release features 119 provide one or more additional hinge points that allow the incremental release of the shaped web material. Preferably, the release features can flex at an angle of up to 45 degrees. Typically a lesser angle of flex will be sufficient to reduce the stress placed on the shaped web material when it is removed from the rotatable tool. This reduction in stress prevents the carrier tape features from becoming skewed or misshaped due to a difficult release from the rotatable tool. The release features do not affect the functionality of the carrier tape and because the release features are located in the crossbars between the pockets, the pocket features do not need to be altered with the addition of the release features. The release features may be any size or shape that allows for easier release of the carrier tape from the rotatable tool. For example, the features may be linear, curved, or a combination of both; continuous or discontinuous; discrete or connected, projections or depressions, etc. They may extend from one edge of the crossbar to the other edge, may extend from one edge to the interior of the cross-bar, or may be located only in the interior of the cross bar. If there is more than one release feature, they may be separated from each other by any suitable distance (which need not be constant between all release features) and may be any suitable number of features. The one or more release features may have any suitable diameter or shape, radii, heights, etc.
FIG. 3 is a digital image of a carrier tape having a first crossbar 310 with an example of release features of the present invention and a second crossbar 312 without a release feature of the present invention. The first crossbars shows multiple ridge and trough release features.
FIG. 4 is a photograph of a cross-sectional view of a carrier tape having a first crossbar 310 with a first example of release features of the present invention, a second crossbar 312 without a release feature of the present invention, and a third crossbar 314 with a second example of release features of the present invention. As can be seen from FIG. 4, the crossbars with the release features are skewed much less than the crossbar with no release feature. Skewing occurs as the carrier tape is removed from the rotatable tool. As can also be seen from FIG. 4, the radii of the ridges and troughs of the first exemplary release features are different from the radii of the ridges and troughs of the second exemplary release features.
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.
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.

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 separated from an adjacent pocket by a crossbar;

wherein at least one crossbar includes at least one release feature.

2. The component carrier tape of claim 1 having multiple release features on at least one crossbar.

3. The component carrier tape of claim 2 wherein the multiple release features differ with respect to one or more of size, shape, height, width, depth, and spacing.

4. The component carrier tape of claim 1 wherein the uppermost portion of the release feature is at or below the plane of the longitudinal flexible strip.

5. The component carrier tape of claim 1 wherein at least one release feature is a trough.

6. The component carrier tape of claim 5 having at least two troughs.

7. The component carrier tape of claim 3 wherein the release features comprise at least two ridges separated by a trough.

8. The component carrier tape of claim 1 wherein the release feature acts as a hinge as the component carrier tape is removed from a forming tool.

9. The component carrier tape of claim 8 wherein the release feature can flex at an angle of up to about 45 degrees.

10. 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; and

wherein a top surface of at least one the crossbar has at least one release feature.

11. A method for producing an embossed carrier tape 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 and at least one patterned depression between adjacent projections for forming at least one crossbar having at least one release feature between adjacent component receiving pockets;

introducing a polymer web onto the tool;

conforming the polymer web against the tool to emboss the web with the projections and depressions on the circumferential surface of the tool; and

removing the embossed web from the tool.