Abstract:
An apparatus and method are provided for using laser energy in an automated bonding machine to effect laser welding of ribbons and other connectors, particularly conductive ribbons in microelectronic circuits. The apparatus and method allow bonding and connection of microelectronic circuits with discrete heating avoiding heat damage to peripheral microelectronic components. The apparatus and method also allow bonding of flexible materials and low-resistance materials, and are less dependant on substrate and terminal stability in comparison to existing bonding methods. The bonding method leads to decreased apparatus wear in comparison to existing bonding methods.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent is a divisional of U.S. patent application Ser. No. 09/688,427 filed Oct. 16, 2000, now U.S. Pat. No. 6,501,043, and claims the benefit of U.S. Provisional Application No. 60/161,103, filed Oct. 22, 1999. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to methods and apparatus for joining connective members, especially conductive members to join electronic and microelectronic circuits. 
     BACKGROUND 
     Electronic circuits, such as microelectronic logic circuits, or other similar electronic circuits, may be fabricated as an integrated unit, which has developed to a highly efficient method of compact circuit manufacture. Ultimately, however, the integrated circuit components or other packaged electronics must be connected to larger circuits in order to be utilized, and be interconnected via lead frames or other connectors with circuits such as input and display apparatus, power supplies and grounds, and complementary circuits. Given the small scale of such circuits, the connection of these circuits also takes place on a relatively small scale. For example, integrated circuit chips are typically less than 0.3 inches×0.3 inches. These circuits may be interconnected by very small wires, e.g. wires with a one mil diameter, or by small, flat conductive metal ribbons which may be, for example, 1×10 mils (0.001 inches×0.01 inches). 
     Generally, metals for electronic connections may be joined by soldering, i.e., by the melting of an alloy or element with a relatively low melting temperature, where neither base material of the joined members is melted or becomes part of the joint. Welding, in contrast, involves the melting of the base members to be joined, resulting in the formation of a weld nugget consisting of material from both of the elements to be joined, in other words, a fusion or thorough and complete mixing between the two edges of the base metal to be joined. 
     While heat is often used to join wires or other conductors together, both for solid-state, fusion, and solder/brazing applications, many traditional methods of heating have proved to have drawbacks in microelectronic applications. One method of applying heat to a bonding site has involved heating the bonding head to convey heat to the bonding site. In an alternate method, a heater block may be clamped to a circuit lead frame. However, heat applied to these structures, which are large relative to the area to be bonded, may cause distortion or bending of the lead frame, or damage to other electrical components. If heat is to be used to solder microelectronic connectors, it would be desirable to more precisely localize this heat on the leads or connectors to be soldered, rather than heating an area as large as, for example, an entire lead frame. 
     As an alternative to soldering using heat alone, ribbon bonders of the prior art have used specialized solid-state bonding methods, e.g., ultrasonic energy, to bond the ribbons to substrates, lead frames, or various electronic components. Ultrasonic energy, a high-frequency vibration, e.g. from 60 KHz to over 100 KHz, is imparted to the parts to be bonded by a bond head. This vibration, and the attendant abrasion of the connector against the terminal pad or lead, in conjunction with heat and mechanical pressure from the bonding head, effects metallurgical atomic diffusion bonding of the connector with the metal of the bonding sites. Modern ultrasonic bonding machines conveniently employ optics and pattern-matching logic systems in order to automate the bonding process for a particular package or circuit being assembled. 
     Ultrasonic ribbon bonding is primarily employed as a method of connecting integrated circuits, packages or substrates in high frequency or high power applications. Ultrasonic bonding techniques, however, have several drawbacks which motivate a reduced reliance on such techniques. Ultrasonic or thermosonic bonding, i.e. ultrasonic vibration using heat, may find application in bonding flat, rigid structures but is not well suited to bonding less rigid, i.e., flexible or semi-flexible structures. Such structures tend to vibrate in response to the ultrasonic energy causing much of the energy to be lost rather than creating the intended bond. Another drawback of ultrasonic bonding is that it may be used primarily with certain materials, and is generally limited to gold, aluminum and copper. Accordingly, the substrate metal to be bonded is generally gold plated. 
     Because the ultrasonic energy is, in fact, a vibration, albeit a very high-frequency one, this vibration may cause undesired movement of the parts to be joined during the bonding process. Not only can this lead to dislocation of the parts vis-à-vis each other, but the movement of the parts during the time when bonding is being effected naturally results in a weaker and inconsistent bond. These problems present substantial vibrational stability requirements for the terminals and substrates used in ultrasonic bonding. In light of the limitations of ultrasonic bonding, an alternative method of bonding conductors for microelectronic devices would be desirable. 
     Resistance welding has enjoyed limited application in microelectronics manufacture. To varying extents, metallic objects resist the flow of electrical current. This resistance will cause heat energy as electric current passes through the metals to be bonded. The higher the amperage and duration of current, the greater the heat energy that will be produced. Metallic objects have thermal properties, a melting point, a specific heat content, thermal conductivity, and more. By using these properties, an environment can be created to produce a molten pool that will harden into a welding nugget. However, the application of resistance welding is limited, and is generally incompatible with low resistance ribbon materials such as copper, silver and gold. 
     Laser-generated heat has found application in certain part-joining methods. For example, lead frames have been soldered with lasers in applications such as TAB (Tape Automated Bonding), utilized, for example, in U.S. Pat. No. 4,893,742 to Bullock. TAB bonding, however, is subject to a number of limitations, chief among them that dedicated and expensive equipment is necessary for each process step. The interconnecting ribbons or leadframes must be formed ahead of time. Therefore, the specially designed tape carriers for each type of circuit being produced involve long lead time and high cost. Dedicated tooling is required to excise and form TAB leads. “Bumping”, i.e., the placement of small metal bumps on the circuit bond sites in order to provide a bonding surface above the circuit&#39;s passivation layer, is required. In addition, the leadframes must be placed and held precisely in position before soldering. Finally, the leads to be bonded with existing apparatus and methods require solder to effect bonding—the main body of the lead and connectors do not reach a melting point, and only the solder is softened. TAB leads are accordingly coated with solder at some point prior to the bonding process. Therefore, considerable advance preparation of the TAB leadframes is required. In general, characterizing the behavior of individual designs and structures is very time-consuming, as is the construction of lead frame tapes for TAB production methods. 
     It would be desirable to provide laser bonding which could be effected using devices similar to traditional wedge bonding equipment, which may automatically bond individual contact points, without the preparation required for tape-mounted lead frames. It would also be desirable to provide a bonding method that would work on a variety of materials, including low-resistance metals, without the use of solder. In addition, it would be desirable to provide a bonding technique that utilizes a highly localized heating area, without peripheral heating of lead frames or other components adjacent the bond site. Finally, it would be desirable to have a bonding method capable of bonding flexible materials that may tend to vibrate in response to the application of ultrasonic energy. 
     SUMMARY OF THE INVENTION 
     Difficulties with existing systems of connector fabrication are overcome with a device providing for laser bonding of ribbon connectors, especially conductive connectors used to provide current pathways for the operation of electronic or microelectronic components. In an alternative embodiment, the device is adapted for use with any material which absorbs the particular wavelength of the laser used. For example, the device may be used to bond non-conductive ribbons, i.e. plastic connectors such as may be used in packaging or other applications. In a further alternative embodiment, the invention may also be used to bond conductive connectors of alternative configurations, e.g. round wire. Preferably, a bonding device according to the present invention utilizes automation as developed for traditional wire and ribbon bonding, e.g. pattern-matching automation. 
     According to one embodiment of the invention, an automated pattern-matching bonder welds one end of an interconnection ribbon, the ribbon being fed from a spool of suitable interconnection ribbon. Subsequently, the bond head of the device moves to the second bond location as it spools out and forms the ribbon into the desired loop shape and then welds the second connection and terminates the ribbon. Alternatively, after formation of a second bond, additional ribbon may be spooled out to form one or more additional loop connectors, each loop terminating at a new weld connection. As an alternative to movement of the bond head, a machine table on which the work piece is mounted may move while the bond head remains stationary. The present invention has potential application for internal device interconnection, i.e., connections internal to an IC package, as well as final board assembly and other microelectronic connections. When bonding is effected according to the present invention, the choices for both ribbon and substrate materials increases, and the dependence on structural rigidity and terminal stability, as required for ultrasonic bonding, decreases or is eliminated. 
     Microelectronic bonding has enjoyed particularly useful application in the implantable medical device art, for example, as demonstrated in U.S. Pat. No. 5,535,097 to Ruben, et al. and U.S. Pat. No. 5,522,861 to Sikorski, et al., both assigned to the assignee of the instant application and both of which are hereby incorporated by reference. By way of example, the present invention may be used to make electrical connectors between and among the hybrid circuit, battery, capacitors, feedthroughs, and other components of implantable medical devices. In addition, however, it will be appreciated to those skilled in the art that the instant invention may be used in various microelectronic applications. These may include, but are not limited to, semiconductor production and chip utilization, integrated circuit packaging and mounting, and other electrical interconnections in the computer hardware and electronics industries. 
    
    
     BRIEF DESCRIPTIONS OF THE DRAWINGS 
     FIG. 1 is a cross-section of part of a ribbon bonding apparatus in accordance with a representative embodiment of the invention. 
     FIG. 2 is a plan view of an aspect of the ribbon bonding apparatus of FIG.  1 . 
     FIG. 3 is an alternate plan view of an aspect of the apparatus of FIG.  2 . 
     FIG. 4 is an alternate plan view of an aspect of the apparatus of FIG.  2 . 
     FIGS. 5-8 illustrate a method of bonding of a ribbon in accordance with an embodiment of the invention. 
     FIG. 9 is a cross-sectional view of a ribbon bonding apparatus according to the present invention. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 depicts a cross-section of a portion of a ribbon bonding apparatus in accordance with a representative embodiment of the invention, the portion being a bond head  100 . A ribbon  102 , such as conductive metal ribbon, is supplied on a standard spool, depicted in a later figure. The bond head  100  is adapted to receive ribbon  102  through a threading slot  104 . Threading slot  104  has a ribbon entrance  104   a  and ribbon exit  104   b . The slot  104  is preferably adapted to admit ribbons of various thicknesses, e.g., 1 mil. From threading slot  104 , ribbon  102  is disposed under bond foot  106 , and may be welded to bond substrate  108  by a laser beam. In embodiments of the subject invention in which the laser is not directed by optic fiber to bond site through bond head  100 , the bond head  100  may be adapted to have a laser aperture  110  to admit laser light that portion of ribbon  102  disposed over bond site  112 . The ribbon may initially be threaded through threading slot  104  in bond head  100 , to ensure proper placement of ribbon  102  relative to bond head  100 . As described herein, the bond head descends to the bond surface and forces the ribbon to contact the substrate or component to be bonded, e.g., an IC bond pad. Once the predetermined load is applied, a laser may be fired in order to weld the ribbon  102  to the substrate  108  or other component. 
     Bond foot  106 , as depicted in FIG. 1, is disposed at the bottom of bond foot  100 , which is shown in plan view in FIG.  2 . As shown in FIG. 2, laser aperture  110  is disposed approximately in the center of bond foot  106 , which turns out from elongate bond head body  114 . These features of bond head  100  are shown in greater detail in plan view in FIG.  3 . The underside of bond head  100  and bond foot  106  is shown in FIG.  4 . As can be seen in FIG. 4, laser aperture  110  is preferably substantially circular in shape, although other shapes suitable for passage of laser energy are possible. Ribbon threading slot  104  has threading slot entrance  104   a , into which ribbon can enter from the back of bond head  100 . Threading slot  104  also has threading slot exit  104   b , from which ribbon may exit while ribbon is being spooled out in connection with loop formation, described herein. 
     A process of connection loop formation according to an embodiment of the present invention is depicted in FIGS. 5-8. In a preferred embodiment of the invention, the bond head has several axes or modes of travel, for example, along an x-axis, y-axis, z-axis (vertically), and theta (rotation). By these various modes of travel as shown in FIG. 5, the bond head  106  may be positioned at a first bond site  112  upon bond surface  116 . The bond head will first descend along the z-axis in order to contact the ribbon  102  to bond surface  116 . Ribbon  102  is therefore disposed between bond foot  106  and bond surface  116 , and thereby held in place. The ribbon  102  is fed through the bond tool ribbon threading slot  104  which holds ribbon  102  in place during bonding. Ribbon  102  may freely pass through ribbon threading slot  104  while bond head  100  travels between first and second or between subsequent bonds or welds. Upon placement of bond head  110  at a first bond site  112 , a predetermined force is applied towards the bond site  112  by the bond head  110 . In one embodiment, the bond head is adapted to receive an optic fiber through its length which allows the laser to fire directly at the point of the weld as depicted in later figures. A suitable laser beam is then fired, for example, through the aperture  110  on the bond foot  106 , heating a portion of the ribbon  102  as well as the bond surface  116  above their respective solidus temperatures. A weld nugget, not depicted, is thus formed at the bond site  112 , the nugget consisting of previously molten material of both the ribbon  102  and bond surface  116 . The weld nugget created by the laser firing may be expected to form a bond of greater strength and reliability than solder or braze bonds. 
     As shown in FIG. 6, following the initial bond as described above, or while the weld nugget of the initial bond is cooling, the bond head  100  may move to a second bond site  120 , such as a programmed site, through an automated or otherwise predetermined trajectory adapted to spool out from bond head  100  a desired length of ribbon  102  to form loop  118 . As shown in FIG. 7, upon contact with a second bond site  120 , ribbon  102  is again disposed between bond foot  106  and bond surface  122 , with a laser firing as before through laser aperture  110  to form a weld nugget at the bond site. Thereafter, further ribbon  102  may be spooled out from ribbon spool in order to form a connected second loop from a continuous length of ribbon. Alternatively, as shown in FIG. 8, ribbon  102  may be terminated by clamping of ribbon  102  above bond head  100  or by locking of the ribbon spool, not depicted. Following clamping of ribbon  102 , bond head  100  is preferably moved in a manner leading to breaking of ribbon  102  in the vicinity of second bond site  120 . In essence, ribbon  102  is terminated by head, table or clamp motions as is typical of existing methods of ultrasonic ribbon bonding. In a preferred embodiment, additional ribbon  102  is played out from a ribbon spool in order to be disposed under bond foot  106  for reinitiation of the bonding process as described above. 
     In an alternate embodiment of the invention, “security welds”, i.e., double or other multiple welds may be effected at each bond site. These security welds serve to increase contact area for improved current flow, mechanical strength, and reliability. The bonder makes the weld, moves slightly and welds the ribbon again to the same terminal. The welds may overlap, may combine to form a single uniform weld nugget, or may be completely separate effecting discrete weld nuggets. 
     While typically described herein and with reference to FIGS. 5-8, as a movement of the bond head from a first bond site to a second bond site, as provided in a preferred embodiment, this bond head motion alternatively may be a relative motion only with regard to the work piece containing bond sites, a work table, or the like. In other words, what is generally termed the bond head motion may be one of or a combination of head, table or work piece movements vis-à-vis each other. 
     In a representative embodiment of the subject invention and as depicted in FIG. 9, a laser beam may be directed at the bond site without passing through the entire length of bond head  110 , thus allowing greater flexibility in motion of the bond head, particularly with regard to  2  (vertical) and theta mode movement (rotation). FIG. 9 depicts a cross section of a portion of a laser bonding apparatus  130  according to the present invention. As illustrated in FIG. 9, a preferred embodiment of the subject invention utilizes a laser, the beam  140  of which is delivered to the bond site  112  through a glass optic fiber  132  to a separate focusing head containing lenses and optics suitable for focusing the laser to bond site  112 ; thereby according full x, y, z, and theta mode movement to bond head  100  without attendant stress on a glass optic fiber  132  that would otherwise extend to bond foot  106  or bond tool  100 . 
     It is believed that methods of laser delivery other than optic fiber running all the way to the bond head may reduce the possibility of certain occurrences such as fiber optic breakage, crimping or splintering of optic fiber  132 . For example, as shown in FIG. 9, an optic fiber  132  may be directed towards the bond site  124 , the optic fiber  132  being located within a separate arm or sheath  136 . Because optic fiber  132  does not extend all the way to bond head  110 , but only to optical fiber/laser housing connector  134 , bond head  110  may be moved according to z (vertical) or theta (rotation) modes without resulting undue stress on optic fiber  132 . Connector  134  joins optic fiber sheath  136  with laser path housing  138 . The laser light beam  140  may be directed at the bond site  124  in a way in which the laser beam is unfocused and consists substantially of light beams traveling parallel to each other. In an alternate embodiment, the laser may be focused, for example, by the use of a lens. In this embodiment of the invention, the focus point  142  of the laser beam  140  may be placed directly at or adjacent the bond site  112 , for example, at the top surface of the ribbon, at the bond surface  116  or slightly below the bond surface  116 . 
     Optic fiber  132  may introduce laser beam  140  to collimating lens  142 , having the effect of spreading out the laser beam into a broader beam. Collimated beam  144  then proceeds to dichroic mirror  146 , where the beam is directed 90 degrees downward towards bond site  124 . Broad beam  144  may be focused by focusing lens  148 , in order to supply a laser focus point  142  at the surface of or at some depth of bond site  124  according to the desired heating effect. 
     By use of dichroic mirror  146 , broad collimated laser beam  140  may be reflected toward bond site  124 . However, camera  150  or other visual sighting accommodation such as an eyepiece for direct viewing may be adapted at top of housing tube  152 , in order to afford viewing for process monitoring, and if desired, other user operations such as manual alignment of focused laser beam  142  through laser aperture  110  and/or manual placement of bond head  100  to desired bond site, e.g., bond site  112 . 
     In a preferred embodiment of the subject invention, bond head  110  and bond head arm  154  may be moved within certain modes of movement, such as x, y, z and theta (rotation) modes, without corresponding or attendant movement of laser housing  138 . Primarily, for example, user may wish to effect movement of bond head  100  and bond arm  154  within the z mode (horizontal or “up and down” movement of the bond head), or theta mode (rotation of bond head  100  relative to bond site  112  or work piece  156  without moving laser housing  138 . In one embodiment of the subject invention, while z mode and theta mode bond head movement is independent of movement of laser housing  138 , movement of bond head  100  according to x and y modes (i.e., planar movement of the bond head along the plane of the work piece) corresponds to an equal movement along the respective x and y mode of laser housing  138 . In other words, in one embodiment laser housing  138  moves in concert with bond head  100  and bond arm  154  in order to maintain vertical alignment of laser focus point  142  with laser aperture  110  of bond head  100 . 
     In an embodiment of the present invention in which laser housing  138  may be moved independently from bond arm  154 , preferably z mode vertical movement of bond head  100  away from bond site  112  will generally be effected only at times when laser beam  140  is not firing. These times generally will be during loop formation, i.e., during the period when ribbon clamp  158  is open, allowing ribbon  102  to feed from spool  160  while ribbon  102  is anchored to a first bond site such as bond site  112  of FIG.  6  and being thus anchored is drawn from spool  160  due to bond head  100  movement away from first bond site  124 , with subsequent termination of bond loop  118  upon bonding of second bond site  120  as depicted in FIG.  7 . In one embodiment of the present invention, an inert cover gas, e.g. helium, argon, or nitrogen is disposed through gas nozzle  162  by jetting over the bond site in order to prevent oxidation or discoloration of bonded ribbon  102 , bond site  112  or the weld nugget. Inert gas jet from gas nozzle  162  also serves to keep lens  148  free of vapors and debris. 
     The bond head  100  may be configured in alternate ways in order to deliver laser beam energy to the bond site. For example, optic fiber  132  may extend directly through bond head  100  and bond foot  106  to bond site  112 . The optic fiber  132  may be completely embedded within bond head  100 , Alternatively, the optic fiber  132  may be free of bond head  100  until entering bond foot  106  in a position corresponding to laser aperture  110  of bond foot  106 . 
     In any of various embodiments of the subject invention, a Nd:YAG 355-1,064 nm laser may be used. Generally, however, the laser source to effect the bonding may be a high power pulsed or continuous wave (CW) laser, e.g. NdYAG, Ar-ion, Carbon dioxide, or Cu vapor. For example, a suitable laser may be a NdYAG Pulsed Laser output of 1 joule/pulse, with a pulse width of 1-5 msec, and a pulse strength of 1000-2000 watts. The power required to generate the required heat is thought typically to be 1-10 watts or more of average power. (A 1 msec, 1000 watt pulse every second would be equivalent to 1 watt of CW operation.) In certain embodiments of the present invention, according to FIG. 9, for example, configured with a carbon dioxide laser, a laser beam may be provided to laser housing  138  directly from a laser beam generator (not depicted) without the use of optic fiber. 
     In addition to ribbon bonding loops between bond pads as described above, this bonding system can also be used to make solder or braze connections between ribbons and substrates. The solder or braze material may already be on the ribbon or substrate or may be an alloy formed during the joining operation. High or low temperature solders and brazes can be used even on temperature sensitive substrates. Because of the very localized heat imparted by laser beam  140 , damage to underlying and adjacent materials is avoided. 
     The bonder could be made as a fully automatic, semi-automatic or manual machine. The difference among these applications would lie primarily in the use of programmability and pattern recognition features, as are currently available in ultrasonic bonding machines of the prior art. The table, ribbon feed and pattern recognition system of an automatic ultrasonic ribbon bonder may be utilized to implement an embodiment of the subject invention. Accordingly, the present invention may be implemented, in certain embodiments, by modification of existing bonding tables and other bonding equipment utilizing automation techniques of circuit manufacture, such as pattern-matching and machine vision technologies. For example, bonding head parts and assemblies are available from various manufacturers, such as Orthodyne Electronics, of Irvine, Calif.; MicroJoin, Inc. (formerly Hughes/Palomar Technologies) of Poway, Calif.; Verity Instruments, Inc., of Carrollton, Tex.; Kulicke &amp; Soffa Industries, Inc. of Willow Grove, Pa.; and F &amp; K Delvotec of Foothill Ranch, Calif. For example, Orthodyne Model 360S Small Wire Bonder or the Delvotec 6400 bonder are thought to provide suitable base units that may provide basic bonding automation functions such as those that may be utilized in accordance with the present invention. 
     In a preferred embodiment of the subject invention, the laser bonding process as described is automated. For example, a device may be presented to the bonder by manual placement on a work holder or automatically by a conveyor system. The position of the device may be determined by pattern recognition, as is known in the art. Preferably, pattern recognition systems and motion algorithms automatically compensate for variations in positions of the bond sites within the various assemblies in order to provide automation of the bonding process. It is believed that, in accordance with a preferred embodiment of the subject invention, throughput of at least one ribbon connection per second may be achieved; equating with two laser firings per second. 
     In one embodiment of the present invention, the above method may be used to bond a nickel-clad copper ribbon 0.002 inches×0.015 inches (2×15 mils). In alternate embodiments of the subject method, ribbons of Pt, Ni 205, Ni 270, and Al 6061 may be laser bonded using the above method. In any embodiment of the invention, materials must adsorb sufficient light from the laser such that their heat is increased above solidus. Certain highly reflective materials may not absorb sufficient laser light to effect sufficient heat rise. 
     It will be appreciated that the present invention, in various embodiments, can be used for soldering, brazing and welding a wider range of materials than possible with resistance welding, ultrasonic welding or soldering alone. It is anticipated that bonds and connections effected according to the instant invention, particularly when effected as security welds, will be highly robust and reliable, and will be significantly more robust and offer a reduced error rate in comparison to existing automated bonding methods. 
     It is believed that a wide variety of connection materials may be suitably bonded by the present invention in one of various embodiments. For example, copper, gold or other ribbon materials could be used. It is anticipated that this will prove particularly useful for non-rigid structures, which are prone to vibration during ultrasonic processes of the prior art. In contrast to bonding systems of the prior art, the present invention requires no special fixation or holding methods or apparatus to hold components in order to eliminate vibration during bonding, because there is no ultrasonic energy to be imparted to the parts to be joined. 
     In further contrast to existing methods of conductive connection bonding, the present invention provides a method of bonding with limited equipment wear and deterioration. For example, ultrasonic bonding equipment, especially for ultrasonic frequencies exceeding 100 KHz, is subject to bond head deterioration resulting from the extreme vibration and frictional forces endured by the bond head. Similarly, resistance welding equipment is subject to electrode wear or oxidation. Furthermore, unlike resistance welding, the present invention admits of bonding low resistance metals such as copper and gold. Gold or copper ribbons are commercially available and preferred for their low resistance, good looping characteristics and corrosion resistance. However, other materials such as nickel and silver could also be welded. 
     While a preferred embodiment of the present invention has been described, it will be appreciated by those skilled in the art that various changes, adaptations and modifications may be made therein without departing from the spirit of the invention and the scope of the appended claims.