WO1999003128A2

WO1999003128A2 - Singulation system for chip-scale packages

Info

Publication number: WO1999003128A2
Application number: PCT/US1998/014078
Authority: WO
Inventors: Phillip E. Koerper; Merlin E. Behnke; Albert J. Chanasyk
Original assignee: Systemation Engineered Products, Inc.
Priority date: 1997-07-09
Filing date: 1998-07-07
Publication date: 1999-01-21
Also published as: WO1999003128A3

Abstract

A singulation system and method for singulating a plurality of chip-scale packages fabricated on a carrier tape is disclosed. The packages are generally rectangular and are arranged in an array having at least one row and a plurality of columns extending in a longitudinal direction. The system includes a first cutting assembly for making first cuts through the tape on first opposite sides of a package in a selected column, the first cuts extending in a transverse direction across the tape. A first positioning mechanism positions the first cutting assembly in a longitudinal direction with respect to the selected column. Drive rollers advance the tape in the longitudinal direction from the first cutting assembly toward a second cutting assembly. The second cutting assembly is for making second cuts through the tape on second opposite sides of the package in the selected column, wherein the second cuts extend in the longitudinal direction and intersect the first cuts. A second positioning mechanism positions the second cutting assembly in the transverse direction with respect to the selected column.

Description

SINGULATION SYSTEM FOR CHIP-SCALE PACKAGES

RELATED APPLICATIONS This application claims the benefit under 35

U.S.C. §119 of co-pending provisional patent applications 60/051,985, filed July 9, 1997 and 60/073,944, filed February 6, 1998.

FIELD OF THE INVENTION

The present invention relates generally to an apparatus and method for singulating a plurality of chip-scale packages, such as micro ball grid array packages, fabricated on a carrier tape.

BACKGROUND OF THE INVENTION The drive for smaller integrated circuit packages has resulted in a number of different package configurations. One category of integrated circuit packages includes chip-scale packages (CSPs), which are generally defined as integrated circuit packages that have an area footprint equal to or less than 1.2 times the footprint of the chip. CSPs are advantageous because their small size makes the circuits useful in applications where size and weight must be low. One type of CSP is a micro ball grid array package, which is a package including an array of solder bumps or balls on a polyimide tape, separated from the face of the integrated circuit chip by a layer of compliant elastomer. The solder balls are connected to the IC chip by interconnections etched on the polyimide carrier film or tape and linked to the die pads of the chip by bond ribbons of gold or copper. A layer of a low modulus encapsulant is used to surround and protect the chip. The micro ball grid array package may also include a soldermask or cover layer. The micro ball grid array packages are intended to be surface mounted on a printed circuit board. The advantages of this package include its robust construction, lack of long leads, and very low profile.

Current manufacturing processes typically result in a plurality of micro ball grid array packages, typically in the form of an array, being produced on a continuous flexible carrier film or tape. The flexible tape thus functions both as a support surface for transporting the micro ball grid array packages through a variety of processing stations and as an integral part of the ball grid array package. The carrier tape is advantageous because it allows the micro ball grid array packages to be transported and handled in a simple and high-speed manner. Subsequent production manufacturing processes, such as laser marking, testing and inspection, may be performed while the packages remain in the array configuration on the tape.

The carrier tape can also be cut into sections or "pages". Each section is pasted to a rigid lead frame to produce a "page" of micro ball grid array packages. A single page may hold approximately 40-60 packages.

The rigid lead frames are also easily transported. In either continuous or page form, the tape allows for greatly simplified handling processes and attendant cost reductions. In order to separate the individual micro ball grid array packages from the carrier film during the final stages of manufacturing, a process denoted "singulation" is required. One prior art technique for performing singulation includes the use of a rigid punch and die apparatus formed as a square or rectangle. Unfortunately, this technique has several drawbacks. One drawback is that since a square cut is made with the shearing action created by square edges, it is difficult to shear through the encapsulant without generating forces that tend to separate the encapsulant from the chip. Additionally, it is difficult to produce and maintain the very square edges of the die necessary to produce the desired square or rectangular singulated package. Furthermore, the clearance required between the punch and die is typically one-half the thickness of the material being cut. For typical micro ball grid array packages, the thickness of one of the materials required to be cut is approximately .001 inch, with a metallization layer of less than .0005 inches. This creates the need to have clearances between the punch and die of less than .0005 inches. This clearance requirement is extremely difficult and expensive to maintain in a production situation.

Another prior art technique involves the use of a cutter similar to a pizza wheel cutter. A sharp rotary blade is used to pierce the material to be cut; causing separation as the blade is rolled. A support surface on the other side of the material guarantees that the cut is made to the required depth. However, this technique is typically performed by first making the longitudinal cuts and then making the transverse cuts across the width of the tape, resulting in a relatively slow process. Furthermore, this technique produces small waste pieces that have to be vacuumed or removed from the area prior to singulating the next packages. Also, because the packages are cut totally loose from the tape, each singulated package must be dealt with independently before the next series of cuts can be made. This also slows down the process, as the only practical method is to pick one package at a time out of the cut array of packages, and place it into a tape or tray. Thus, the "pick and place" process steps are required to be merged into the singulation process steps.

One advantage of the pizza cutter technique is that it is possible to program the positioning of the blade to accommodate different sized parts to be cut, ensuring that no hard tooling changes are required between different sized packages. However, since opposite sides of the package are being cut at different times, it is more difficult to maintain the proper overall dimensions of the singulated package.

Another prior art singulation technique is called "singulation by shearing". This technique uses cutting blades that are similar in cutting action to that performed by a pair of scissors. Two sets of opposing blades are used so that the width of the cut is reasonably accurate. In this case also, separate longitudinal and transverse cuts are necessary. Similar to the previously described pizza cutter technique, this technique also results in the production of many waste pieces. Additionally, a clean cut is difficult to obtain.

Industries other than the semiconductor fabrication industry have long used rule die technology to cut paper or labels, for example. Rule dies are generally segments of a long rule material upon which a sharp edge is ground. The segments are held in a hardwood block by inserting them into laser-cut slits in the block. The rule die operates to make a cut by descending through a material until the die makes contact with or "kisses" a back-up platen. The back-up platen keeps the material to be cut in position.

Rule die technology has heretofore not been used in the semiconductor industry in part because the technology has not been considered sufficiently accurate to cut within a thousandth of an inch. Additionally, cutting complete packages from a tape requires very sharp, reliable cutting edges for the square corners. The cutting edges are difficult to achieve and maintain, especially with a low-skilled work force. Further, cutting through multiple layers of materials has been difficult and generally not the accepted practice because of the potential for incomplete cutting. To summarize, rule die technology is generally considered an inexpensive process incapable of meeting the demanding accuracy requirements of the semiconductor industry. SUMMARY OF THE INVENTION It is an object of the present invention to provide an apparatus and method for singulating chip- scale packages from a flexible carrier tape in an accurate manner, while achieving low stresses to prevent the encapsulant surrounding the semiconductor device or the interface between the encapsulant and the device from being damaged. It is a further object of the present invention to provide an apparatus and method for singulating chip scale packages from a flexible carrier tape in a low cost manner, at a high rate of speed, wherein the process is easy to maintain. It is a further object of the present invention to provide an apparatus and method for singulating chip scale packages wherein the transverse and the longitudinal cuts are performed separately such that the cuts overlap but the cutting process generates no waste pieces.

The invention provides a singulation system and method for singulating a plurality of chip-scale packages fabricated on a carrier tape. The packages are generally rectangular and are arranged in an array having at least one row and a plurality of columns extending in a longitudinal direction. The system includes a first cutting assembly for making first cuts through the tape on first opposite sides of a package in a selected column, the first cuts extending in a transverse direction across the tape. A first positioning mechanism positions the first cutting assembly in a longitudinal direction with respect to the selected column. Drive rollers advance the tape in the longitudinal direction from the first cutting assembly toward a second cutting assembly. The second cutting assembly is for making second cuts through the tape on second opposite sides of the package in the selected column, wherein the second cuts extend in the longitudinal direction and intersect the first cuts. A second positioning mechanism positions the second cutting assembly in the transverse direction with respect to the selected column.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic diagram of a singulation system for singulating chip-scale packages in accordance with the present invention;

Fig. 2 is an illustration of one side of a page of micro ball grid array packages fabricated on a flexible tape and showing the arrays of solder balls;

Fig. 3 is an illustration of a second side of the page of micro ball grid array packages;

Fig. 4 is a perspective view of a portion of the singulation system in accordance with the present invention illustrating one embodiment of the infeed module;

Fig. 5 is a perspective view from a different angle of the singulation system and infeed module illustrated in Fig. 4; Fig. 6 is a perspective view of the singulation system illustrating a second embodiment of the infeed module;

Fig. 7 is a perspective view from a different angle of the singulation system illustrated in Fig. 6; Fig. 8 is a perspective view of a cassette for holding a plurality of pages;

Fig. 9 is a top view of a portion of the singulating module;

Fig. 10 is an elevational view of a portion of the singulating module;

Fig. 11 is a perspective view of a portion of the singulating module;

Fig. 12 is a perspective view of the longitudinal cutting assembly; Fig. 13 is another perspective view of the longitudinal cutting assembly;

Fig. 14 is a perspective view of the upper platen of the longitudinal cutting assembly; Figs 15 is a perspective view of the transverse cutting assembly;

Fig. 16 is another perspective view of the transverse cutting assembly; Fig. 17 is another perspective view of the transverse cutting assembly;

Figs. 18 and 19 are perspective views of the upper platen of the transverse cutting assembly;

Fig. 20 is an illustration of the transverse and longitudinal cuts made around a column of packages;

Figs. 21 (a) -21 (i) are illustrations of various views of the picker device of the present invention;

Figs. 22 - 24 illustrate the picker device in a picking configuration, showing a plan view and elevational views;

Fig. 25 is a top view of the singulating module and the conveyor system;

Fig. 26 is an elevational view of the singulating module and the conveyor system; Fig. 27 is a perspective view of the singulating module and conveyor system;

Figs 28(a) and (b) are illustrations of different blade cross-sections.

Before one embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components or steps set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various other ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

DESCRIPTION OF THE PREFERRED EMBODIMENT Illustrated in Fig. 1 is a schematic diagram of a singulation system 10 for singulating chip-scale packages. The singulation system 10 includes an infeed module 12, a singulating module 14, and an output module 16. The modules are mounted on a frame (not shown) and are arranged with respect to one another generally as shown in the diagram. The singulating module 14 includes various stations such as a plurality of drive rollers 18, 20, 22, 24, 26, two deskew stations 28, 30, a transverse cutting assembly 32, a longitudinal cutting assembly 34, a longitudinal positioning mechanism 36, a transverse positioning mechanism 38, two camera assemblies 40, 42, a frame reject assembly 43, and a column pick and place assembly 44. The output module 16 includes a conveyor system 46 having a plurality of boats, a single pick and place assembly 50, and storage devices 52 such as trays for storing the individual singulated packages.

A general description of the operation of the singulation system 10 is as follows. The infeed module 12 handles one or more cassettes each containing a plurality of pages. As shown in Fig. 8, a cassette (or magazine) 54 holds a plurality of pages 56 in a vertical stack. The cassette 54 has two interior surfaces 53 each having a plurality of horizontally extending ledges 55. The pages 56 are oriented generally horizontally one above the other and are supported on the ledges 55. The infeed module 12 operates to sequentially feed one page at a time from the cassette 54 to a transport path 68 (shown in Fig. 9) in the singulating module 14. As shown in Figs. 2 and 3, each page 56 is constructed of a portion of flexible tape 58 attached along two edges 59 to a rigid lead frame 60. The flexible tape 58 includes a plurality of micro ball grid array packages 62 fabricated thereon in an array configuration. The array configuration of the packages 62 on the page 56 illustrated consists of five rows and twelve columns; however, various other array configurations are also common and can be accommodated by the singulating module 14.

The solder balls 88 for each package are typically arranged in a regular array or grid 90 of standard ball pitch, such as 1.0 mm or .75 mm, with the solder balls typically placed within the footprint area of the integrated circuit chip itself. In the singulating module 14, each page 56 is oriented such that the ball arrays 90 face down. However, another embodiment is also contemplated wherein the ball arrays face up and the camera assembly is located above the base plate 15. As illustrated in Fig. 3, on the opposite side of the page from the solder balls are the exposed back sides of each integrated circuit chip 62. The RTV silicone-encapsulant 92 surrounds the perimeter of each chip.

The lead frame 60 has a series of perforations 57 along its two edges 61. The drive rollers 18, 20, 22, 24, 26, of the singulating module 14 grip the edges 61 of the page to move the page 56 along the transport path 68 from the infeed module 12 to the output module 14. The deskew stations 28, 30 sense the position of the leading edge 64 of the page (or perforations 57 along the edges 61 of the page), and operate to align the page 56 against a longitudinally extending guide rail 70 at two points along the transport path. The first deskew station 28 is located preceding the transverse cutting assembly 32 on the transport path 68, and the second deskew station 30 is located preceding the longitudinal cutting assembly 34 on the transport path 68.

The transverse cutting assembly 32 and the longitudinal cutting assembly 34 of the singulating module 14 are operable to achieve accurate, complete cutting around the boundaries of each package 62 on a page 56. The transverse cutting assembly 32 operates to generate all transverse cuts, while the longitudinal cutting assembly 34 operates to generate all longitudinal cuts. As used herein, the longitudinal direction is the direction of page travel along the transport path 68, and the transverse direction is generally perpendicular to the longitudinal direction. The longitudinal direction is along the x-axis illustrated in Fig. 9, and the transverse direction is along the y-axis.

The transverse cutting assembly 32 and the longitudinal cutting assembly 34 are located longitudinally spaced apart from each other along the transport path 68 and are operable simultaneously to provide cuts to different pages at one time (although simultaneous operation is not required) . Both assemblies 32, 34 include respective cutting blades 71, 72 (shown in Figs. 14 and 18) that are slightly longer than the length or width of the desired singulated package such that at each package corner 63, the longitudinal cut and the transverse cut generated by the blades overlap to ensure a complete cut. For example, illustrated in Fig. 20 are the transverse cuts 116 and the longitudinal cuts 118 for a column of packages. The cuts do not extend across more than one package 56, and no waste pieces are generated during the cutting process. In addition, an alternative within this invention is to use the same construction and arrangement as explained in the preceding paragraph except that the cutting assemblies 32 and 34 are spaced apart such that they can simultaneously make cuts on different columns on the same page. That is, as transverse cutting assembly 32 makes transverse cuts on one column and the longitudinal cutting assembly 34 makes longitudinal cuts on another column but on the same page. These cuts are made simultaneously (although simultaneous operation is not required) and on adjacent columns

(although the columns being cut need not be adjacent). The page, or tape, is then indexed so that additional transverse and longitudinal cuts are made until the entire page has the requisite cuts to cut all of the packages 62 on the page.

Referring to both Figs. 1 and 20, the camera assemblies 40, 42 are located underneath the cutting assemblies 32, 34. Each camera assembly 40, 42 operates to sense the position of the micro ball grid array packages 62 on the page with respect to the respective cutting assembly. Thus, the cutting blades 71, 72 can be aligned with respect to the respective sides 74, 76, 78, 80 (shown in Fig. 20) of the packages to insure that the cuts occur in the correct location. The longitudinal positioning mechanism 36 operates to align the transverse cutting blades 71 in the longitudinal direction with respect to the two side edges 74, 76 of the packages. Similarly, the transverse positioning mechanism 38 aligns the longitudinal cutting blades 72 transversely with respect to the top and bottom edges 78, 80 of the packages. In the preferred embodiment, the transverse cutting blades 71 cut parallel to the side edges 74, 76 of a single column of the packages at a time. Also, the longitudinal cutting blades 72 cut parallel to the top and bottom edges 78, 80 for a single column of packages at a time.

The column pick and place assembly 44 includes a picker device 82 having a set of fingers 84 (illustrated in Figs. 21(a)-(i)). After the transverse cuts 116 have been successively made for all the columns on the page, the page is fed forward, and the longitudinal cuts 118 are made. After the longitudinal cutting blades 72 produce the longitudinal cuts 118 for each column of packages, the packages 62 in that column are removed from the tape 58. In particular, after the longitudinal cutting blades produce the cuts, the blades are lifted upwardly, and the packages are lifted out of the tape with the blades a column at a time. As the longitudinal cuts are made, the fingers 84 are moved between the longitudinal cutting blades 72. A vacuum is applied to the fingers 84, and the packages are stripped from between the blades 72.

After all the packages have been removed from a page, the frame reject assembly 43 ejects the page into a wastebin.

As shown in Fig. 25, from the column pick and place assembly 44, the packages 62 are transported to a boat 48 and are released from the fingers 84 and placed into pockets 49 in the boat 48. The boats 48 are transported by the conveyor system 46 between the column pick and place assembly 44 and the single pick and place assembly 50. The boats 48 are loaded with packages 62 by the column pick and place assembly 44 and unloaded by the single pick and place assembly 50. The single pick and place assembly 44 operates to lift a single package at a time out of the boat 48, rotate the package by ninety degrees, and place it into a storage device 52. Fig. 4 illustrates a perspective view of one embodiment of a portion of the singulation system 10 (not including the single pick and place assembly 50). Note that the singulation system 10 may include protective covers 94 for various parts of the singulating module 14 and conveyor system 46. The covers include access doors 96, which can be opened and closed.

Figs. 4 and 5 also illustrate in detail a particular embodiment of the infeed module 12. The infeed module 12 operates to sequentially feed one page 56 at a time from a cassette 54 to the first set of drive rollers 18 in the singulating module 14. The infeed module 12 can hold one or more cassettes 54. The infeed module 12 includes a frame assembly 98 having a longitudinally extending pusher arm 100, a vertically extending track 102, and a support member 104 that is vertically movable in the track 102. Functionally, the cassette 54 rests on the support member 104 and is aligned such that the top page in the cassette is even with the transport path 68. The pusher arm 100 is actuated by a pneumatic slide 106 and operates to push the top page horizontally along the transport path 68 to the drive rollers 18. The support member 104 is vertically movable in the track by a stepper motor 108. After the pusher arm 100 pushes the top-most page in the cassette 54 to the singulating module 14, the support member 104 and cassette 54 are moved vertically upwards so that the next page is horizontally aligned with the transport path 68. This process is repeated to feed successive pages to the singulating module 14. Figs. 6 and 7 illustrate a second embodiment of the infeed module 12. A greater number of cassettes can be accommodated at one time in this second embodiment. The frame assembly 110 is formed in a C- shape. The cassettes 54 are moved in a path from the bottom portion 112 of the C, upwards along the vertical portion 113 (where the pusher arm 100 operates), then out along the top portion 114 of the C. Although the travel paths of the cassettes themselves in the two embodiments of the infeed modules are different, the operation of the pusher arm 100 and support member 104 is similar in both embodiments.

The singulating module 14 illustrated in Figs. 9, 10 and 11 will now be described in greater detail. In the preferred embodiment, the singulating module 14 includes various stations supported on a base plate 15. In particular, as best seen in Figs. 9 and 10, the module includes five sets of drive rollers 18, 20, 22, 24, 26 spaced along the transport path 68, which extends from left to right in the figures. Each page is successively fed to the first set of drive rollers 18 by the infeed module 12. The first deskew station 28 is located next to the first set of drive rollers 18 along the transport path 68. The first deskew station 28 includes a longitudinally extending guide rail 70 and a push bar 69 that operates to push the page transversely against the guide rail 70. The second set of drive rollers 20 assumes control of the page once the leading edge 64 of the page has advanced far enough along the transport path 68. The second set of drive rollers 20 operates to feed the page to the transverse cutting assembly 32. After the transverse cuts are made, the third set of drive rollers 22 together with the second deskew station 30 and the fourth set of drive rollers 24 operate to feed the page to the longitudinal cutting assembly 34. After the longitudinal cuts are made, and the packages have been removed from the tape by the column pick and place assembly (discussed below), the fifth set of drive rollers 26 feeds the empty page to an ejection area 120 of the frame reject assembly 43. In the ejection area 120, a set of ejecting arms 122 operate to push the empty page in a transverse direction and into a wastebin 124.

As best seen in Figs. 12 and 15, both the transverse cutting assembly 32 and the longitudinal cutting assembly 34 include an upper platen 126 and a lower platen 128. For both assemblies 32, 34, the cutting blades are mounted in the upper platen 126 and the upper platen 126 is moved downwardly with respect to the lower platen 128 to accomplish the cutting. The lower platens 128 include a primary surface 134 comprising a semi-rigid material, such as "stainless steel 303", nylon, delrin, or a similar material, which is softer than the blades 71, 72. In addition to these materials, composites and spray coatings on some of these materials are also contemplated.

The blades 71, 72 contact the primary surface 134 at specific respective blade mating surfaces 136, 138 during the cutting process. As shown in Fig. 15, the blade mating surfaces 136 of the transverse cutting assembly 32 extend transversely. As shown in Fig. 12, the blade mating surfaces 138 of the longitudinal cutting assembly 34 extend longitudinally. For both cutting assemblies 32, 34, the initial location of the lower platen 128 with respect to the upper platen 126 is not critical. However, it is important to maintain the same relationship between the blades 71, 72 and the respective lower platen 128 in order to assure that the blades contact the lower platen at the respective blade mating surfaces 136, 138 so that the lower platen 128 is not slowly degraded. To accomplish this, the upper 126 and lower platens 128 are tied together by the use of dowel pins 140 in a fixture 142 such that the platens 126, 128 can move vertically with respect to each other, but not along the x-axis or the y-axis. Illustrated in Figs. 17-19 are the upper platen

126 of the transverse cutting assembly 32 and the cutting blades 71. The blades 71 are arranged parallel to the y-axis. In the preferred embodiment, the transverse cuts are made for one column of packages at a time. The two transverse cutting blades 71 include notches 130 to produce separate blade portions which produce the individual transverse cuts 116 (shown in Fig. 20). For a page having five rows, there are five packages in each column, so each blade 71 is notched to produce five equally spaced blade portions. By producing notches 130 in the blades 71 to generate the separate blade portions, the alignment of each blade portion with the others is automatically accomplished. In the preferred embodiment, the upper platen 126 comprises a solid block of steel with slots manufactured by means of an EDM process. The blades 71 are inserted in these slots and held in position with compressive members 143. The position of the cutting edge of the blade is maintained to within .0005 inches. Similarly, illustrated in Fig. 14 is the upper platen 126 of the longitudinal cutting assembly 34 and the longitudinal cutting blades 72. The blades 72 are arranged parallel to the x-axis. In the preferred embodiment, the longitudinal cuts are made for one column of packages at a time. The arrangement of the longitudinal cutting blades 72 includes ten separate blades to make ten separate longitudinal cuts 118 around the five packages in a column. The upper platen 126 of the longitudinal cutting assembly 34 includes a blade mounting surface 132 and two diverging surfaces 131 and 133. The upper platen 126 includes slots manufactured by an EDM process. The blades 72 are inserted in these slots and held in place with members mounted on surfaces 131, 133.

Of course, it is also contemplated that different blade arrangements be used to effect cutting around a different number of packages at one time. For example, it may be desirable to cut more or less than one column of packages at a time. Whatever the blade arrangement, preferably the blades cut at least two opposite sides of a package at the same time.

A conventional cutting blade fabricated from commercially available rule die material cut into suitable lengths would have a symmetrical cross- section, as shown in Fig. 28(a). However, in the preferred embodiment, the blades are fabricated using commercial rule dies that are stainless steel, hardened, and precision ground to produce a blade having a cutting edge with an asymmetrical cross section, as illustrated in Fig. 28(b). The blade is mounted in the upper platen so that the beveled edge faces away from the package side to be cut. Using the blade shown in Fig. 28(b), it is possible to obtain a clean cut when the distance between the blade and the chip is no more than three or four thousandths of an inch.

The two sets of blades 71, 72 together cut around a column of packages without cutting completely across the tape. As shown in Fig. 20, the cuts generate no waste pieces. Also, the longitudinal and transverse cuts overlap at the corners 63 of the singulated packages because the length of each blade is slightly greater than the desired length or width of the singulated package. This larger blade size prevents incomplete cuts. Additionally, the exact length of the blade is not critical. The decoupling of the transverse and longitudinal cuts means that the longitudinal positioning of the transverse blades with respect to the package is important, while the transverse position of the transverse blades is less so. Similarly, with respect to the longitudinal blades, the transverse positioning of the longitudinal blades with respect to the package is important while the longitudinal position of the longitudinal blade is not as critical. In other words, it is important to effect accurate longitudinal positioning of the transverse blades with respect to the package on the tape in order to create accurately aligned side edges of the singulated package. It is also important to effect accurate transverse positioning of the longitudinal blades with respect to the package on the tape in order to create accurately aligned top and bottom edges of the singulated package.

To accomplish the positioning, either the page 56 or the respective cutting assembly 32, 34 may be moved relative to the other. In the preferred embodiment, the page 56 is held fixed and the respective cutting assemblies 32, 34 are accurately moved in a direction transverse to their respective blades 71, 72. The lower platen 128 of the transverse cutting assembly 32 is movable in a vertical direction between a lowered position and a raised position. The lower platen is moved to the lowered position when a page is driven along the transport path 68 so that there is clearance between the longitudinally moving solder balls 88 and the transversely extending blade mating surfaces 136. The lower platen 128 also includes pockets 152 that provide clearance for the solder balls 88 when the lower platen 128 is moved to the raised position. In the raised position, the lower platen 128 supports the page 56 during the cutting process. The lower platen 128 is raised and lowered with four pneumatic cylinders.

The lower platen also includes a hole 154 to permit a portion of the bottom of the page 56 to be viewed from underneath system 10. In operation, the lower platen 128 is moved to its lowered position as a page is fed to the transverse cutting assembly 32 and rough alignment of the page 56 with respect to the transverse cutting assembly 32 is achieved. Light through a fiducial hole in the tape 58 is detected by a sensor to provide an indication of rough alignment. The lower platen 128 is moved to the raised position once the page is roughly aligned. The camera assembly 40 then determines the fine alignment necessary for the appropriate position of the blades 71 with respect to the package 62. More specifically, referring to Figs. 10 and 11, each camera assembly 40,42 is mounted underneath its respective cutting assembly 32, 34. Each camera assembly 40, 42 includes a camera positioning track 156, a camera 158 oriented to point upward, a light source (not shown), and a controller (not shown). A hole in the base plate 15 and the hole in the lower platen 126 allows the camera 158 to be focused on the solder balls 88 of the center package of a specific column of packages 62 on the page 56. The light source underneath the system 10 provides additional light for the camera 158 to obtain a adequate image of the bottom side of the page 56.

The controller calculates the longitudinal offset and communicates with the longitudinal positioning mechanism 36 to move the transverse cutting assembly 32 along the x-axis as necessary so that the cutting blades 71 align with the two sides 74, 76 of the center package. At this time, the lower platen 128 has been moved to its raised position and remains stationary as the upper platen 126 is lowered and the transverse cuts 116 are made. The process is then repeated to make the transverse cuts 116 for the next adjacent column and so on for the entire page.

One way to effect positioning of the cutting assembly 32 with respect to the tape is to use the solder balls 88 as reference marks. For example, the solder balls 88 on the tape can be viewed through grid lines on the camera 158. The transverse cutting assembly 32 is moved longitudinally with respect to the page 56 until the solder balls 88 are transversely centered between two transversely extending grid lines. The transverse cutting assembly 32 is moved via the longitudinal positioning mechanism 36, which includes a stepper motor. Once the transverse cutting assembly 32 is correctly positioned, the blades 71 are lowered to effect the transverse cuts.

Once the transverse cuts have been made for a specific column, because the cuts do not extend transversely across the more than one package, no material is removed in the cutting process and the singulated packages, although cut, are held in place by the tape. As shown in Fig. 12, for the longitudinal cutting assembly 34, the blade mating surfaces 138 extend longitudinally, so that a set of longitudinally extending lower surfaces 160 provide clearance for the solder balls 88 as a page 56 moves through the longitudinal cutting assembly 34. Vertical movement of the lower platen 126 is therefore unnecessary. Again, a hole 154 through the lower platen 128 and base plate 15 permits a portion of the bottom side of the page to be viewed from underneath system 10. In this case, the controller calculates both the transverse and longitudinal offset. The controller communicates the transverse offset to the transverse positioning mechanism 38 to move the longitudinal cutting assembly 34 along the y-axis as necessary so that the cutting blades 72 align with the top 78 and bottom edges 80 of the center package. At this time, the upper platen 126 is lowered and the longitudinal cuts are made. The process is then repeated to make the longitudinal cuts for the next adjacent column, and so on for the entire page. The longitudinal offset determined by the controller is used to position the picker device 82 of the column pick and place assembly 44, as described below.

It is also contemplated that instead of the cutting assemblies 32, 34 being positioned relative to a package on the tape, the cutting assemblies would be positioned with respect to another mark on the tape itself. For example, one of the perforation edges could serve as a reference mark, or the interconnections etched on the tape could also serve as a reference mark.

Figs. 25-27 illustrate the column pick and place assembly 44 and the conveyor system 46 with boats 48. These pieces of the singulation system 10 are also mounted on a base plate 17. As previously described, after the transverse cuts 116 have been successively made for all the columns on a given page, the page is fed forward, and the longitudinal cuts 118 are made. After the longitudinal cutting blades 72 produce the longitudinal cuts 118 for each column of packages 62, the packages 62 in that column are lifted by the cutting blades 72 as the upper platen is raised and the packages 62 are stripped from the blades 72 by the column pick and place assembly 44. The column pick and place assembly 44 places the packages in a boat 48. The conveyor system 46 moves the boats around on an endless conveyor. A boat is stationary as it is filled with packages at point 146, then is incrementally advanced to point 148, where the packages are unloaded. An optional vision system 162 including a camera can inspect the packages in the pockets of the boats as the boats 48 travel to point 148.

Referring in particular to Fig. 24, the column pick and place assembly 44 includes a picker device 82, a transport device 144, a longitudinally extending track 146, and a stepper motor (not shown) to move the transport device 144 towards and away from the longitudinal cutting assembly 34. Another stepper motor moves the transport device 144 vertically up and down to lower the packages when they are to be unloaded in a boat 48.

The picker device 82 is illustrated in detail in Figs. 21(a)-21(i) and is generally L-shaped. The picker device 82 includes an upright member 164 and a horizontal member 166 with a plurality of horizontally extending fingers 84. The fingers 84 are sized to fit between the longitudinal cutting blades 72. The upright member 164 includes means for fastening the picker device 82 to the transport device 144. The upright member 82 also includes an air port 170 connectable to an air passage that extends vertically and connects with horizonal air passages 172 extending through each finger 84. At each finger tip 174, the air passages open to air ports 176. The air port 170 is adapted to be connectable to a source of pressurized air and a vacuum.

The picker device 82 is movable to a picking configuration. The picking configuration is shown in Figs. 22-24. In the picking configuration, the fingers 84 are moved between the longitudinal cutting blades 72. The longitudinal offset determined by the controller as previously described for the longitudinal cutting assembly 34 is used to determine the longitudinal extent of travel of the picker device 82 towards the cutting assembly 34. In this manner, the picker device 82 is longitudinally positioned directly above the column of cut packages. At this point, the vacuum is applied to the air port 170 to create a vacuum at air port 176, and the longitudinal cutting blades 72 make the longitudinal cuts. The column of packages 62 is lifted from the page 56 via the finger tips 174. As the longitudinal cutting blades 72 are lifted upwardly after the cuts have been made, the packages 62 are lifted out of the tape 58 by the picker device 82 and are transported away from the cutting assembly 34.

Referring again to Fig. 25, the singulated packages 62 are then lowered to place the packages in a boat 48. In order to ensure alignment between the packages and a boat 48, the transport device 144 has two conical indentations (not shown) that match two conical projections 178 on each boat 48. As the transport device 144 is lowered, the conical projections gently guide the transport device 144 to mate with the boat 48. Each boat also includes a plurality of pockets 49 shaped to hold an individual package. A puff of air is applied to the fingertips of the picker device 82, and the packages 62 are released from the finger tips and dropped into the pockets 49.

The boats 48 are transported by the conveyor system 46 between the column pick and place assembly 44 and the single pick and place assembly 50. The boats 48 are unloaded by the single pick and place assembly

50. In order to align the boats with the picker of the assembly 50, an alignment apparatus 180 is used. As best shown in Fig. 27, a wedge shaped projection 182 mates with an indentation along a top surface of the boat.

The single pick and place assembly 44 operates to lift a single package at a time out of the boat 48, rotate the package by ninety degrees, and place it into a storage device 52. Such an assembly is conventional and is fully covered in another patent application. It is understood that the invention is not confined to the particular construction and arrangement of parts herein illustrated and described, but embraces all such modified forms thereof as may come within the scope of the following claims. It will be apparent that many modifications and variations are possible in light of the above teachings. It therefore is to be understood that within the scope of the appending claims, the invention may be practiced other than is specifically described. Alternative embodiments and variations of the invention taught in the present specification may suggest themselves to those skilled in the art upon reading of the above description.

Claims

CLAIMSWhat is claimed is:

1. A method for singulating a plurality of chip- scale packages fabricated on a carrier tape, wherein the packages are generally rectangular and arranged in an array having at least one row and a plurality of columns extending in a longitudinal direction, the method comprising: aligning a first cutting assembly with a selected column on the tape, using the first cutting assembly to make first cuts through the tape on first opposite sides of a package in the selected column, the first cuts extending in a first direction, advancing the tape in the longitudinal direction toward a second cutting assembly, aligning the second cutting assembly with the selected column on the tape, and using the second cutting assembly to make second cuts through the tape on second opposite sides of the package in the selected column, the second cuts extending in a second direction transverse to the first direction.

2. The method as recited in claim 1, wherein the second cuts overlap the first cuts.

3. The method as recited in claim 1, wherein the second direction is substantially perpendicular to the first direction.

4. The method as recited in claim 1, wherein the first cuts are in the transverse direction across the tape and the second cuts are in the longitudinal direction.

5. The method as recited in claim 4, wherein the first cutting assembly includes first blade portions extending in the transverse direction, and the first blade portions are longitudinally aligned with the package in the selected column before the first cuts are made.

6. The method as recited in claim 5, wherein the second cutting assembly includes second blade portions extending in the longitudinal direction, and the second blade portions are transversely aligned with the package in the selected column before the second cuts are made.

7. The method as recited in claim 1, wherein the first cuts are in the longitudinal direction and the second cuts are in the transverse direction across the tape.

8. The method as recited in claim 7, wherein the first cutting assembly includes first blade portions extending in the longitudinal direction, and the first blade portions are transversely aligned with the package in the selected column before the first cuts are made.

9. The method as recited in claim 8, wherein the second cutting assembly includes second blade portions extending in the transverse direction, and the second blade portions are longitudinally aligned with the package in the selected column before the second cuts are made.

10. The method as recited in claim 1, wherein the package when singulated has a desired length and a desired width, and each first cut is slightly greater than the desired width, and each second cut is slightly greater than the desired length.

11. The method as recited in claim 1, wherein the package when singulated has a desired length and a desired width, and each first cut is slightly greater than the desired length, and each second cut is slightly greater than the desired width.

12. The method as recited in claim 1, wherein the step of aligning a first cutting assembly with a selected column on the tape includes using a first camera assembly to determine the position of a mark on the package with respect to the first cutting assembly.

13. The method as recited in claim 12, wherein the first cutting assembly makes first cuts in the transverse direction across the tape, and the first cutting assembly is longitudinally aligned with the mark on the package.

14. The method as recited in claim 13, wherein the step of aligning a second cutting assembly with a selected column on the tape includes using a second camera assembly to determine the position of the mark on the package with respect to the second cutting assembly.

15. The method as recited in claim 14, wherein the second cutting assembly makes second cuts in the longitudinal direction, and the second cutting assembly is transversely aligned with the mark on the package.

16. The method as recited in claim 1, further including the step of sequentially feeding a plurality of portions of tape to the first cutting assembly.

17. The method as recited in claim 1, wherein the first cuts and the second cuts extend across only one package.

18. A method for singulating a plurality of chip-scale packages fabricated on a carrier tape, wherein the chip-scale packages are generally rectangular and arranged in an array having at least one row and a plurality of columns extending in a longitudinal direction, the method comprising: aligning a first cutting assembly having first blade portions longitudinally with respect to a selected column on the tape, using the first blade portions to make first cuts through the tape on first opposite sides of a package in the selected column, the first cuts extending in a transverse direction across the tape, advancing the tape in the longitudinal direction toward a second cutting assembly having second blade portions, and aligning the second blade portions transversely with respect to the selected column on the tape, and using the second blade portions to make second cuts through the tape on second opposite sides of the package in the selected column, the second cuts extending in a longitudinal direction, wherein the second cuts intersect the first cuts, wherein the chip- scale package when singulated has a desired length and a desired width, each first cut is slightly greater than the desired width, and each second cut is slightly greater than the desired length.

19. The method as recited in claim 18, further including the steps of moving a finger mechanism between the second blade portions as the second blade portions are removed from the tape, applying a vacuum to the finger mechanism to remove the package from the tape.

20. The method as recited in claim 19, further including the steps of transporting the package to a boat and releasing the package from the finger mechanism into the boat.

21. The method as recited in claim 20, further including the step of unloading the boat using a single pick and place assembly to place the package in a storage device.

22. A singulation system for singulating a plurality of chip-scale packages fabricated on a carrier tape, wherein the packages are generally rectangular and arranged in an array having at least one row and a plurality of columns extending in a longitudinal direction, the system comprising: a first cutting assembly for making first cuts through the tape on first opposite sides of a package in a selected column, the first cuts extending in a first direction, a first positioning mechanism for positioning the first cutting assembly in a second direction with respect to the selected column, the second direction substantially perpendicular to the first direction, means for advancing the tape in the longitudinal direction, a second cutting assembly for making second cuts through the tape on second opposite sides of the package in the selected column, the second cuts extending in the second direction, and a second positioning mechanism for positioning the second cutting assembly in the first direction with respect to the selected column.

23. The singulation system as recited in claim 22, wherein the second cuts overlap the first cuts.

24. The singulation system as recited in claim 22, wherein the first cuts are in the transverse direction across the tape and the second cuts are in the longitudinal direction.

25. The singulation system as recited in claim

24, wherein the first cutting assembly includes first blade portions extending in the transverse direction, and the first blade portions are longitudinally aligned with the package in the selected column before the first cuts are made.

26. The singulation system as recited in claim

25, wherein the second cutting assembly includes second blade portions extending in the longitudinal direction, and the second blade portions are transversely aligned with the package in the selected column before the second cuts are made.

27. The singulation system as recited in claim 22, wherein the first cuts are in the longitudinal direction and the second cuts are in the transverse direction across the tape.

28. The singulation system as recited in claim

27, wherein the first cutting assembly includes first blade portions extending in the longitudinal direction, and the first blade portions are transversely aligned with the package in the selected column before the first cuts are made.

29. The singulation system as recited in claim

28, wherein the second cutting assembly includes second blade portions extending in the transverse direction, and the second blade portions are longitudinally aligned with the package in the selected column before the second cuts are made.

30. The singulation system as recited in claim 22, wherein the package when singulated has a desired length and a desired width, and each first cut is slightly greater than the desired width, and each second cut is slightly greater than the desired length.

31. The singulation system as recited in claim 22, wherein the package when singulated has a desired length and a desired width, and each first cut is slightly greater than the desired length, and each second cut is slightly greater than the desired width.

32. The singulation system as recited in claim 22, further including a first camera assembly for determining the position of a mark on the package with respect to the first cutting assembly.

33. The singulation system as recited in claim 32, wherein the first cutting assembly makes first cuts in the transverse direction across the tape, and the first cutting assembly is longitudinally aligned with the mark on the package.

34. The singulation system as recited in claim 33, further including a second camera assembly for determining the position of the mark on the package with respect to the second cutting assembly.

35. The singulation system as recited in claim 34, wherein the second cutting assembly makes second cuts in the longitudinal direction, and the second cutting assembly is transversely aligned with the mark on the package.

36. The singulation system as recited in claim 22, further including means for sequentially feeding a plurality of portions of tape to the first cutting assembly.

37. The singulation system as recited in claim 22, wherein the first cuts and the second cuts extend across only one package.

38. A singulation system for singulating a plurality of chip-scale packages fabricated on a carrier tape, wherein the packages are generally rectangular and arranged in an array having at least one row and a plurality of columns extending in a longitudinal direction, the system comprising: a first cutting assembly for making first cuts through the tape on first opposite sides of a package in a selected column, the first cuts extending in a transverse direction across the tape, a first positioning mechanism for positioning the first cutting assembly in a longitudinal direction with respect to the selected column, means for advancing the tape in the longitudinal direction from the first cutting assembly toward a second cutting assembly for making second cuts through the tape on second opposite sides of the package in the selected column, the second cuts extending in the longitudinal direction and intersecting the first cuts, and a second positioning mechanism for positioning the second cutting assembly in the transverse direction with respect to the selected column.

39. The singulation system as recited in claim 38, wherein the package when singulated has a desired length and a desired width, and each first cut is slightly greater than the desired width, and each second cut is slightly greater than the desired length.

40. The singulation system as recited in claim 38, wherein the second cutting assembly includes blade portions and further including a vacuum finger mechanism movable between the blade portions and operable to apply suction to the package and remove the package from the tape.

41. The singulation system as recited in claim 40, wherein the vacuum finger mechanism is operable to release the package.

42. The singulation system as recited in claim 41, further including a boat to receive the package from the vacuum finger mechanism.

43. The singulation system as recited in claim 42 further including a single pick and place device for unloading the package from the boat and placing the package in a storage device.

44. A method for singulating a plurality of chip- scale packages fabricated on a carrier tape, wherein the packages are generally rectangular and arranged in an array having at least one row and a plurality of columns extending in a longitudinal direction, the method comprising: aligning a first cutting assembly with a selected column on the tape, using the first cutting assembly to make first cuts through the tape on opposite sides of a package in a selected column, the first cuts extending in a first direction, aligning the second cutting assembly with a selected column on the tape, using the second cutting assembly to make second cuts through the tape on second opposite sides of the package in a selected column, the second cuts extending in a second direction transverse to the first direction, advancing the tape in the longitudinal direction, and using the first and second cutting assemblies to make additional first and second cuts on the columns in said carrier tape.

45. The method as recited in claim 44 wherein the first cuts are on first opposite sides of a package and the second cuts on second opposite sides of a package.

46. The method as recited in claim 45 wherein said first and second cuts are made simultaneously.

47. The method as recited in claim 46 wherein the columns being cut are adjacent.

48. The method as recited in claim 47 wherein the second direction is substantially perpendicular to the first direction.

49. The method as recited in claim 48, wherein the first cuts are in the transverse direction across the tape and the second cuts are in the longitudinal direction.