WO2010065335A1

WO2010065335A1 - Method of making a component carrier tape

Info

Publication number: WO2010065335A1
Application number: PCT/US2009/065255
Authority: WO
Inventors: Shiow Shya Ling; Kam Poi Chia; . Anthonius
Original assignee: 3M Innovative Properties Company
Priority date: 2008-12-03
Filing date: 2009-11-20
Publication date: 2010-06-10
Also published as: TW201028351A

Abstract

Provided is a flexible carrier tape having multiple pockets for storage and delivery of components, the carrier tape being made by providing a web of a flexible thermoplastic polymer formed into the shape of a carrier tape having multiple pockets and exposing the bottom wall of each pocket to a cutting tool to form a vacuum slit in the bottom wall.

Description

METHOD OF MAKING A COMPONENT CARRIER TAPE

TECHNICAL FIELD

This invention relates generally to carrier tapes for transporting components from a component manufacturer to a different manufacturer that assembles the components into new products.

BACKGROUND

In general, carrier tapes for transporting components from a component manufacturer to a different manufacturer that assembles the components into new products are well known. For example, in the field of electronic circuit assembly, electronic components are often transferred from a source of such components to a specific location on a circuit board for attachment thereto.

Carrier tapes are often manufactured in a thermoforming operation in which a web of thermoplastic polymer is delivered to a mold that forms the component pockets. The thermoformed web is usually cooled to ambient temperature. There is a tendency for components to flip or jump out of the pocket, thus a vacuum hole is incorporated in the bottom of the pocket. This vacuum hole is used to hold down the components while the carrier tape is being indexed by applying a negative pressure to the hole, which holds the component against the bottom of the pocket.

However, as the components get smaller and lighter, there are increased incidences of components flipping and jumping out of the pocket, even when the pocket includes a vacuum hole.

The conventional method of producing this vacuum hole is by mechanically punching through the base of the carrier tape. With the increasing miniaturization of electronic components, the existing punching method faces its manufacturability limitation. In addition, punching creates waste (slugs) and dust that may contaminate the components, which can be of special concern when manufacturing precision electronic parts. In addition, the thermoplastic web may be a tough, resilient material that can be difficult to punch. As a result, the punches wear out or break and have to be frequently replaced. Precision punches are expensive and replacing them is a time consuming process that requires delicate realignment and retiming of the new punch. SUMMARY

One aspect of the present invention relates to a method of making a flexible carrier tape for storage and delivery of components, the carrier tape comprising a plurality of pockets for carrying the components, the method comprising: (a) providing a web of a flexible thermoplastic polymer formed into the shape of a carrier tape having multiple pockets; (b) exposing the bottom wall of each pocket to a cutting tool to form a vacuum slit in the bottom wall.

Another aspect of the present invention relates to a carrier tape comprising a series of pockets, each pocket having at least a front side wall, a back side wall, and a bottom wall, wherein the bottom wall contains a vacuum slit.

An advantage of at least one embodiment of the present invention is that it provides carrier tapes that can accommodate small components while also allowing for high vacuum pulling power on the components due to the high aspect ratios and large total areas of the vacuum openings.

An advantage of at least one embodiment of the present invention is that it provides precisely formed vacuum openings in carrier tapes.

An advantage of at least one embodiment of the present invention is that it allows for increased productivity in the carrier tape manufacturing process. An advantage of at least one embodiment of the present invention is that it provides a process for forming vacuum openings in carrier tapes that is easy to set up, easy to maintain, and creates less debris than some prior art processes.

As used in this application, "vacuum hole" means an opening in the bottom wall of a carrier tape pocket having a 1 : 1 aspect ratio. As used in this application, "vacuum slit" means an opening having greater than a

1 : 1 aspect ration in the bottom wall of a carrier tape pocket.

As used in this application, "aspect ratio" means the ratio of width to height with the width being the longest dimension regardless of the orientation of the vacuum slit on the bottom wall of the carrier tape pocket. BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a further understanding of embodiments and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments and together with the description serve to explain principles of embodiments. Other embodiments and many of the intended advantages of embodiments will be readily appreciated as they become better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding similar parts.

FIG. IA is a fragmentary top perspective view of a prior art carrier tape with a cover thereof having been partially removed to show components stored within the carrier tape; FIG. IB is a fragmentary bottom perspective view of the carrier tape of FIG. IA;

FIGS. 2A-2C are fragmentary bottom perspective views of various embodiments of a carrier tape of the present invention.

FIG.3 is an illustration of a method of the present invention.

DETAILED DESCRIPTION In the following Detailed Description, 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. In this regard, directional terminology, such as "top," "bottom," "front," "back," "leading," "trailing," etc., is used with reference to the orientation of the Figure(s) being described. Because components of embodiments can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration and is in no way limiting. 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.

Turning now to the drawings, FIGS. IA and IB illustrate a prior art carrier tape with a vacuum hole 118. The illustrated carrier tape 100 has a strip portion 102 defining a top surface and a bottom surface opposite the top surface. Strip portion 102 includes longitudinal edge surfaces 104 and 106, and a row of aligned advancement structures 108 and 110 formed in and extending along one, and preferably both, edge surfaces.

Advancement structures 108 and 110 provide a means for engagingly receiving an advancement mechanism. A series of pockets 112 is formed in and spaced along strip portion 102, as shown in FIG. IA, the pockets opening through the top surface of the strip portion. In the illustrated embodiment, each pocket 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 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 102. As shown in FIG. IB, bottom wall 116 includes a vacuum hole 118 which is used in applying a vacuum to the pocket to permit more efficient loading of the pockets with components. In general, pockets 112 are designed to conform to the size and shape of the components that they are intended to receive. 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 that adjoins and extends downwardly from strip portion 102, and a bottom wall that adjoins the side wall to form the pocket. Thus, the pockets may be circular, oval, triangular, pentagonal, or have other shapes in outline. Each side wall may also be formed with a slight draft (i.e., a 2° to

12° slant toward or away from the center of the pocket) in order 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 pocket may be formed with ledges, ribs, pedestals, bars, mils, appurtenances, and other similar structural features to better accommodate or support particular components. Although a single column of pockets is illustrated in the drawings, two or more columns of aligned pockets could also be formed along the length of the strip portion in order to facilitate the simultaneous delivery of multiple components. It is expected that the columns of pockets would be arranged parallel to each other with pockets in one column being in aligned rows with the pockets in the adjacent column(s).

Strip portion 102 may be formed of any polymeric material that has a sufficient gauge and flexibility to permit it to be wound about the hub of a storage reel. A variety of polymeric materials may be used including, but not limited to, polyester (e.g., glycol- modified polyethylene terephthalate), polycarbonate, polypropylene, polystyrene, polyvinyl chloride, and acrylonitrile-butadiene-styrene. Strip portion 102 may be optically clear, pigmented or modified to be electrically dissipative. In the latter case, the strip 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 strip. 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.

Carrier tape 100 typically further includes an elongate cover 120, although its inclusion is optional. Cover 120 is applied over the pockets of the carrier tape to retain the components therein. As best shown in FIGS. IA and IB, cover 120 is flexible, overlies part or, more preferably, all of pockets 112, and is disposed between the rows of advancement structures 108 and 110 along the length of strip portion 102. Cover 120 is releasably secured to the top surface of strip portion 102 so that it can be subsequently removed to access the stored components. As illustrated, cover 120 includes parallel longitudinal bonding portions 122 and 124 that are bonded to longitudinal edge surfaces 104 and 106, respectively, of strip portion 102. 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.

FIG. 2 A illustrates an embodiment of the present invention in the form of carrier tape 200. It is similar to prior art carrier tape 100 except that instead of vacuum holes 118 in the bottom walls 116 of pockets 112, carrier tape 200 of the present invention comprises vacuum slits 228 in the bottom 216 of pockets 212. Although the vacuum slits in FIG. 2A extend the full length (front to back) of pockets 212 and also extend partway into front and back side walls 214, in other embodiments, vacuum slits 228 may be smaller such that they only extend over a portion of the length of pocket 212. FIGS. 2B and 2C show examples of embodiments of the present invention having partial vacuum slits. In FIG.

2B, vacuum slit 228 extends through part of bottom wall 216 and through one side wall 214 (either the front or back side wall could include vacuum slit 228). In FIG. 2C, vacuum slit 228 extends only through part of bottom wall 216 and does not extend through either the front or back side wall 214. Furthermore, vacuum slits 228 may be oriented in any direction on the bottom wall 216 of the pockets 212. For ease of production, slits oriented in the longitudinal direction of the carrier tape 100 are typically preferred. According to prior art methods, a punching tool is used to mechanically punch out vacuum holes 118 in the bottom walls 116 of the carrier tapes 100. The punching tool has a series of adjacent punching pins that punch holes in several adjacent pockets at once. The punching pins must be precisely spaced apart so that each pin punctures the bottom wall 116 of a pocket 112 at an appropriate location. Manual alignment of each punching pin is done to ensure proper alignment to the critical feature of the carrier tape. Regular maintenance and refurbishing are required to ensure the sharpness of tool to provide cleanly punched hole.

According to a method of the present invention, a single rotating or stationary tool can be used to continuously create openings in the pocket bottoms of a carrier tape. The method allows faster set up and also consistency of the formed openings. Minimal maintenance and refurbishing are required due to the better properties of the cutting tool. The method of the present invention includes aligning a cutting tool with the bottom of the carrier tape pockets and bringing the cutting tool into contact with each successive pocket bottom on a continuous basis. This can be done in a number of ways. The cutting tool may be linear or round and may be stationary or movable. The cutting tool may be moved while the tape stays stationary; the tape may be moved while the cutting tool stays stationary; or both the cutting tool and the tape may be moved. Vacuum openings may be formed in the bottom walls of carrier tape pockets in a batch process, i.e., vacuum openings are formed in a group of adjacent pockets at the same time, then the continuous carrier tape web is advanced and vacuum openings are formed in a second group of adjacent pockets at the same time, and so on. Alternately, and preferably, vacuum opening are formed in one pocket bottom after another on a continuous basis, i.e., the continuous carrier tape web (or the cutting tool) continuously moves at a constant speed as each subsequent pocket bottom is brought into contact with the cutting tool.

In one embodiment of the invention, a linear blade, such as a knife blade, may be drawn across a series of pocket bottoms in a stationary carrier tape to create slits in each pocket. In another embodiment, the pocket bottoms of a carrier tape may be drawn over a stationary round blade to create slits in each pocket. In yet another embodiment, a rotary cutting tool having a circular moving blade, such as a tool used to dice semiconductor wafers, may be operated while the pockets of a carrier tape are passed over the rotating circular blade of the rotary cutting tool. A suitable rotary cutting tool is a dicing saw such as the one available under the trade designation DFD6340 from DISCO Corporation, Japan.

When the pockets are brought into contact with the cutting tool, the carrier tape may be held flat or may be held in a curved position. If the carrier tape is held in a curved position, the bottom surface 216 of the individual pockets will be spaced further apart from each other than when the carrier tape is held in a flat position. The arc of the curved position, as well as the size and shape of the cutting tool, will partially determine how many pockets are simultaneously in contact with the cutting tool. If the arc is large, many pockets may contact the cutting tool at the same time. If the arc is small, it may be possible to bring a single pocket at a time into contact with the cutting tool. To achieve the partial vacuum slits shown in FIGS. 2B and 2C, it may be necessary to bring a single pocket at a time into contact with the cutting tool. The partial vacuum slits of FIGS. 2B and 2C may also be achieved if the cutting tool is a rotary tool 500 having an arc substantially smaller than the arc of the carrier tape 200, as is illustrated in FIG. 3. A benefit of the partial vacuum slits is that the pocket retains a substantial amount of structural support while also providing a vacuum feature.

The carrier tapes of the invention are particularly useful in the electronics industry for transporting and delivering electronic components such as memory chips, integrated circuit chips, resistors, connectors, dual in-line processors, capacitors, gate arrays, capacitors, etc. However, the carrier tapes of the invention may also be used to transport other small components that are typically delivered to precision placement machines such as watch springs, small screws, surface mount electric component shields, and the like.

The present invention has now been described with reference to several embodiments thereof. It will be apparent to those skilled in the art that many changes can be made in the embodiments described without departing from the scope of the invention. Hence, the scope of the present invention shall not be limited by the structures described herein, but only by structures described by the language of the claims and the equivalents of those structures.

Claims

CLAIMS:

1. A method of making a flexible carrier tape for storage and delivery of components, the carrier tape comprising a plurality of pockets for carrying the components, the method comprising: (a) providing a web of a flexible thermoplastic polymer formed into the shape of a carrier tape having multiple pockets;

(b) exposing the bottom wall of each pocket to a cutting tool to form a vacuum slit in the bottom wall.

2. A method according to claim 1 wherein the cutting tool is a rotary tool.

3. A method according to claim 1 wherein the cutting tool is a linear tool.

4. A method according to claim 1 wherein the carrier tape is bent into an arc shape as the bottom walls of the pockets are exposed to the cutting tool.

5. A method according to claim 1 wherein the cutting tool is held stationary and the carrier tape is moved against the cutting tool.

6. A method according to claim 1 wherein the carrier tape is held stationary and the cutting tool is moved against the carrier tape.

7. A method according to claim 1 wherein both the cutting tool and the carrier tape are moved against each other.

8. A method according to claim 7 wherein the cutting tool and carrier tape are moved in opposite directions against each other.

9. A method according to claim 2 wherein the rotary cutting tool is a rotating circular blade.

10. A method according to claim 3 wherein the linear cutting tool is a straight-edged blade.

11. A carrier tape comprising a series of pockets, each pocket having at least a front side wall, a back side wall, and a bottom wall, wherein the bottom wall contains a vacuum slit.

12. The carrier tape according to claim 11 wherein the vacuum slit extends over at least a portion of the back wall and partway into at least one of the front side wall and the back side wall.

13. The carrier tape according to claim 11 wherein the vacuum slit extends over the entire length of the back wall and partway into both the front side wall and the back side wall.

14. The carrier tape according to claim 11 wherein the vacuum slit extends over only a portion of the back wall and does not extend into either the front side wall or the back side wall.