Tool drive apparatus

A tool drive apparatus and method are provided which are particularly well suited for the processing of semiconductor chips on leadframe strips. The tool drive apparatus includes at least one press having a tool-receiving space, a top and bottom tool received in the tool-receiving space, and a drive unit coupled to the at least one press for asynchronous substantially vertical movement of the top tools in adjacent presses. The drive unit includes a rotatable main shaft carrying up to six cam discs each of which may be associated with a press. This arrangement permits the processing of more than one process area on a leadframe strip in the same press cycle in one tool at a time enabling the tools to be placed closer together to shorten the processing line. The tool drive apparatus may also include a latch assembly which, when activated, creates a larger tool-receiving space for repair and maintenance of the tool in one press without affecting other presses in the processing line.

FIELD OF THE INVENTION
 This invention relates generally to cutting, trimming and forming systems
 for producing semiconductor devices and, more specifically, to a tool
 drive apparatus and method for use thereof for asynchronous operation of
 the system tools.
 BACKGROUND OF THE INVENTION
 In a production line for packaging semiconductor chips (the term
 "semiconductor chip" or "chips" has been used interchangeably herein with
 the terms "semiconductor devices" and "semiconductor packages"), a wire
 bonding operation is used to create wire bonds between portions of
 semiconductor chips and selected portions of associated leadframe strips.
 The output of semiconductor chips after the wire bonding operation is
 inputted into a molding portion or step. The molding step encapsulates
 semiconductor chips in plastic. The encapsulated semiconductor chips and
 their associated leadframe strips leaving the molding step enter a post
 mold curing and cool down step.
 Following curing and cooling of the encapsulated semiconductor chips, a
 dambar cutting and debris removal step removes dambars from the leadframe
 strips and dislodges excess debris from the plastic housing for each of
 the semiconductor chips. A plating step or operation plates selected
 portions of the leadframe strips with a selected plating material while an
 off-load/on-load step is between the dambar cutting and debris removal
 step and the plating step. The output from the plating step is inputted
 into a trim and form step or operation that both removes excess portions
 from the leadframe strips by cutting and shapes portions of the leadframe
 strips by bending extended leads thereof extending from the semiconductor
 chips. A marking step or operation typically follows in which the plastic
 housing for each semiconductor chip is marked with an identification
 designation. The marking step may alternatively be done before the plating
 step. The offload section of the trim and form/marking steps or operation
 delivers each of the assembled and completely packaged semiconductor chips
 to magazines. The above steps are each typically performed by stand-alone
 systems. A leadframe strip may be configured to include a single row of
 semiconductor chips or it may be configured as a multi-row (matrix)
 configured leadframe strip. A process area on a leadframe strip includes
 one or more semiconductor chips depending on leadframe strip
 configuration.
 Conventional processing has included a linear track along which has been
 positioned one press having a top press plate and a bottom press table,
 between which is a tool house for each tool performing a step of the
 process. As the leadframe strip travels along the track, the top press
 plate typically moves vertically opening and closing the press. The tools
 have disadvantageously been operated simultaneously i.e. one could not
 close one tool at a time because top press plate movement affects all the
 tools. Previously, all the packages (plastic encapsulated semiconductor
 chips) on one leadframe strip had to go through a first tool by moving
 forward one process pitch at a time before reaching a second tool.
 Leadframe strip transport and press movement have typically been
 controlled by software sequences one movement at a time.
 In order to position each leadframe strip correctly within each station
 performing the various steps, each leadframe strip contains alignment
 holes that match corresponding alignment pins in the supporting equipment,
 with which they become engaged for proper positioning at each portion.
 These same alignment holes are used as the leadframe strip progresses
 along the track for processing. Since each step is carried out within very
 narrow tolerances, it is extremely important that these alignment holes,
 particularly the center thereof, remain in constant spatial relationship
 with respect to the rest of the leadframe strip. Moreover, it is important
 that the alignment holes are not damaged during leadframe strip transport
 or during positioning inside a tool. Unfortunately, the plastic molding
 step subjects the leadframe strip to structural and thermal stresses
 caused by differences in the heat expansion coefficients of the metal and
 the plastic material. Thus, during the cooling phase, the plastic
 encapsulated leadframe strip is stressed by the cooling plastic and is
 subjected to bending, waving and twisting of the leads as well as
 shrinkage causing leadframe strip pitch changes and warping or tensioning
 of the leadframe strips. This deformation often results in a misalignment
 of the alignment holes in the leadframe strip with the receiving pins in
 successive workstations, which causes a mismatch between the holes and the
 pins causing considerable quality control problems.
 Because of the foregoing structural and thermal stresses, the tendency
 toward more precision devices with smaller dimensions, more exacting
 tolerances and a matrix configured leadframe strip has led to the
 conclusion that a leadframe strip must be processed progressively instead
 of at once. Moreover, each leadframe strip can be processed by only one
 tool at a time to prevent positioning of the leadframe strip by more than
 one tool.
 Therefore, tools in one press should have been positioned a minimum of
 about 250 mm apart from each other (assuming a maximum leadframe strip
 length of 250 mm). However, tool accuracy worsens and production costs
 increase the longer the distance from tool to tool. Moreover, the amount
 of production floor space required by these arrangements is extensive,
 particularly when necessary to process a number of leadframe strips at the
 same time.
 Accordingly, there has been a need for a novel tool drive apparatus and
 method to accurately process more than one process area on a leadframe
 strip in the same press cycle. There is an additional need for a tool
 drive apparatus and method that enable tools to be placed closer together
 than the length of a leadframe strip so as to shorten the processing line
 taking up only a fraction of the previously-used production floor space to
 lower costs and to increase accuracy and efficiency. A still further need
 exists for a tool drive apparatus and method that offers more processing
 flexibility, higher throughput, and that can be quickly and inexpensively
 retooled to perform different processing steps at each station to process
 different types of leadframe strips as well as process different
 semiconductor packages. There is a still further need for a tool drive
 apparatus and method to be used with a drive unit that operates more than
 one press and that only uses the force to drive the tool that has the
 heaviest process operation. Additionally, there is a need for a tool drive
 apparatus and method in which the leadframe strip can be positioned in one
 tool at a time. The present invention fulfills these needs and provides
 other related advantages.
 SUMMARY OF THE INVENTION
 It is an object of this invention to provide a tool drive apparatus and
 method to accurately process more than one process area on a leadframe
 strip in the same press cycle.
 It is an additional object of this invention to provide a tool drive
 apparatus and method that enable tools to be placed closer together so as
 to shorten the leadframe strip processing line taking up only a fraction
 of the previously-used production floor space to lower costs and to
 increase accuracy and efficiency.
 It is a still further object of this invention to provide a tool drive
 apparatus and method that offers more processing flexibility, higher
 throughput, and that can be quickly and inexpensively retooled to perform
 different processing steps at each station to process different types of
 leadframe strips as well as process different packages.
 It is a still further object of this invention to provide a tool drive
 apparatus and method with a drive unit that operates more than one press
 and that only uses the force to drive the tool that has the heaviest
 process.
 It is yet another object of this invention to provide a tool drive
 apparatus and method in which the leadframe strip can be positioned in one
 tool at a time.
 The tool drive apparatus comprises, generally, at least one press having a
 tool-receiving space, a top and a bottom tool received in the
 tool-receiving space of each of the at least one press, and a drive unit
 coupled to the at least one press for asynchronous movement of the top
 tools of adjacent presses. Each of the at least one press may include a
 latch assembly for increasing the tool-receiving space.
 The at least one press may assume either a processing position (top tool is
 at a position where the leadframe strip is physically processed during a
 press cycle) or a non-processing position (the Lop tool is at a higher
 position where the leadframe strip cannot be touched during a press
 cycle).
 The at least one press includes a base block adapted to be placed on the
 drive unit. The base block includes a lower substantially box-like portion
 and an upstanding elongated portion at the rear thereof. An upper surface
 of the substantially box-like portion supports a stationary bottom tool
 table. A top tool table is separated from the bottom tool table by a
 plurality of guide pillars. The top tool table is physically connected and
 moved by a top tool lever. The top tool table moves vertically while
 maintaining a substantially parallel relationship to the bottom tool
 table.
 The tool-receiving space between the bottom and top tool tables receives a
 tool including a bottom tool and a top tool. Each tool has a standard
 bottom and top set and a dedicated bottom and top product-related set. The
 bottom and top tools are separated by a pair of guide pillars, shorter in
 length than the guide pillars separating the bottom and top tool tables.
 The top tool lever preferably has a generally A-shaped platform with a wide
 front portion and a narrower rear portion. The top tool table and top tool
 lever are interconnected at the front portions thereof by a lower and an
 upper pair of joint blocks and a pair of pivot joints.
 The top tool lever extends rearwardly to a position outboard and rearwardly
 of the upstanding elongated rear portion of the base block. The rear end
 of the top tool lever is pivotally connected to an upper end of an H-beam
 shaped rear push rod that forms part of the latch assembly. The rear push
 rod extends downwardly from the top tool lever.
 The latch assembly further includes an air cylinder. The air cylinder
 includes an upper and a lower air inlet. The air cylinder is outboard of
 and substantially parallel with the rear push rod. The air cylinder also
 includes a retractable piston rod therein, the lower end thereof connected
 to a latch. The latch includes an upper and lower clevis pivotally
 interconnected to opposite ends of a push arm back. A pair of retraction
 springs extends on opposite sides of the rear push rod at a position
 proximate the lower end of the air cylinder to an upper end of a
 curvewheel lever.
 The at least one press is driven by the drive unit. The drive unit includes
 a motor coupled to a main shaft. The main shaft preferably carries up to
 six cam discs, each of which may be associated with a press. Of course, a
 greater number of cam discs and presses are within the scope of this
 invention. A curvewheel is resiliently urged by a compression spring to
 follow the associated cam disc. The curvewheel rotates the curvewheel
 lever causing the associated press to open and close.
 The cam discs are all the same with each including a key-way.
 Asynchronization between adjacent presses is achieved by varying the
 rotational position of the cam discs relative to one another on the main
 shaft. The relative rotational position of the cam discs is realized by
 offset milling of the key slots in the main shaft i.e. the key slots of
 the main shaft are milled out of line. The rotational position of the cam
 disc driven by the main shaft determines whether the respective cam disc
 is in "tool-down" position or "tool-up position".
 Each cam disc also has a curve or grind with a slope for fast movement
 (e.g. for cutting) and a slope for slow movement (e.g. for bending). The
 press follows the total curve of the cam disc. The height of the tool
 determines which point of the curve is being used as the starting point
 for processing the leadframe strip.
 When the press is in a processing mode and the motor is driven, the main
 shaft will rotate causing the cam discs to likewise rotate and the
 curvewheel to follow causing adjacent presses to open and close
 asynchronously. In the processing mode, the upper and lower devises are
 vertically aligned with the push arm back and the piston rod is retracted
 into the air cylinder. The air cylinder and rear push rod are also
 substantially vertically aligned or upright. Therefore, in the processing
 mode, the latch assembly is like a "rigid" beam. The top tool lever will,
 during a press cycle, move between a generally horizontal position and a
 slightly rotated position. The rear push rod moves substantially
 vertically and rotates the top tool lever pushing or pulling the top tool
 table and associated top tool vertically. The pair of retraction springs
 maintains the latch assembly in this processing position.
 In order to put a press into the non-processing position, the latch
 assembly of that press is activated by forcing air through the upper inlet
 of the air cylinder. The air forces extension of the piston rod from the
 air cylinder rotating the lower clevis downwardly and rearwardly to a
 collapsed position with the lower end of the rear push rod and the air
 cylinder becoming disposed at an outward angle to the rest of the press.
 As the latch assembly collapses, the top tool lever rotates quickly
 lifting the top tool table. The plurality of guide pillars guide the top
 tool table during the lift. A shock absorber substantially prevents shock
 and serves as the end-position when the top tool lifts quickly. The pair
 of retraction springs maintains the latch assembly also in the collapsed
 position. With the top tool out of the way in the raised position, repairs
 or maintenance thereon can be done without interfering with other presses.
 To return the press to the processing position, air is forced into the
 lower inlet of the air cylinder to return the latch assembly to the
 substantially vertically-aligned configuration.
 Other features and advantages of the present invention will become apparent
 from the following more detailed description, taken in conjunction with
 the accompanying drawings which illustrate, by way of example, the
 principles of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 As shown in the drawings for purposes of illustration, the present
 invention is concerned with a tool drive apparatus and method, the
 apparatus generally designated in the accompanying drawings by the
 reference number 10. The tool drive apparatus 10 comprises, generally, at
 least one press 12 having a tool-receiving space 14, a top and a bottom
 tool 16 and 18 received in the tool-receiving space 14 of each of the at
 least one press 12, and a drive unit 20 (See FIG. 2) coupled to the at
 least one press 12 for movement of the top tools 16. Each of the at least
 one press 12 may include a latch assembly 22 (see FIG. 3) for increasing
 the tool-receiving space 14.
 In accordance with the present invention, and as illustrated with respect
 to a preferred embodiment in FIGS. 1 through 14, the tool drive apparatus
 10 permits each tool to have its own press movement. This arrangement
 permits more than one process area within one leadframe strip 24 to be
 processed by more than one tool in the same press cycle. The leadframe
 strip 24 may be a single row (FIGS. 9a and 9b) or a multi-row (matrix)
 configured leadframe strip 24 (FIG. 9c). The process area may include one
 or more semiconductor chips 26 depending on the size of the semiconductor
 chips (see FIGS. 9a-9c). The accuracy and positioning problems formerly
 associated with leadframe strip processing are substantially avoided and
 production floor space decreased as the tools can be positioned relatively
 close to each other. The at least one press 12 may assume either a
 processing position (top tool 16 is at a position where the leadframe
 strip 24 is physically processed) or a non-processing position (the top
 tool 16 is at a higher position where the leadframe strip 24 cannot be
 touched), as hereinafter described.
 The at least one press 12 includes a base block 28 (see FIG. 10) adapted to
 be placed on the drive unit 20. The base block 28 includes a lower
 substantially box-like portion 30 and an upstanding elongated portion 32
 at the rear thereof terminating at an upper end in a pair of abutments 34.
 An upper surface of the substantially box-like portion 30 supports a
 stationary bottom tool table 36.
 A top tool table 38 is separated from the bottom tool table 36 by a trio of
 upstanding guide pillars 40 arranged in a triangle, each guide pillar 40
 fixed at one end in a rear portion of the bottom tool table 36 and
 extending upwardly therefrom to a corresponding rear portion of the top
 tool table 38. The apex of the triangle is at the rear edge of the bottom
 and top tool tables 36 and 38. This arrangement permits a very rigid tool
 table set (in X and Y directions). Of course, it is to be understood that
 a greater or lesser number of guide pillars 40 may be used within the
 confines of the invention. As shown in FIGS. 3 and 4, the guide pillars 40
 guide the top tool table by a caged ball bearing assembly 42 and a bearing
 raceway 44, preferably made from steel. A bushing 45, preferably made from
 plastic, below the bearing raceway 44 substantially prevents the caged
 ball bearing assembly 42 from coming out of the bearing raceway 44. The
 top tool table 38 is physically connected and moved substantially
 vertically while maintaining a substantially parallel relationship to the
 bottom tool table 36 by a top tool lever 46, as hereinafter described. The
 guide pillars 40 assist in maintaining this movement vertically accurate.
 As shown in FIGS. 6 and 7, the tool-receiving space 14 between the bottom
 and top tool tables 36 and 38 receives a tool including a bottom tool 18
 and a top tool 16. The bottom tool 18 includes, in ascending order from
 the bottom tool table 36, a bottom tool adapter plate 48, a bottom tool
 standard set 50, and a bottom tool product-related (dedicated) set 52.
 From the top tool table 38, the top tool 16 includes in descending order a
 top tool adapter plate 54, a top tool standard set 56, and a top tool
 product-related (dedicated) set 58. The term "product" herein refers to a
 semiconductor chip, semiconductor package or semiconductor device. Each
 tool has these standard top and bottom sets and a dedicated top and bottom
 product-related set. The leadframe strips 24 are processed in the space
 between the bottom and top product-related sets 52 and 58. For cutting,
 trimming and forming systems for producing semiconductor chips, exemplary
 tools include a dambar cut tool, a leadframe cutting tool, a leadframe
 bending tool, and a singulation tool. Other tools may, of course, be used
 as well as other processes within the spirit of the invention.
 The bottom and top tools are separated by a pair of relatively short guide
 pillars 60. The short guide pillars 60 are fixed in the top tool 16 in
 much the same manner as the Longer guide pillars 40 are fixed in the
 bottom tool table 36. The shorter guide pillars 60 guide the top tool by a
 caged ball bearing 63 and a bearing raceway 61. The term "relatively" here
 refers to the longer guide pillars 40. The relatively short guide pillars
 60 are for accurate positioning of the top tool 16 in relation to the
 bottom tool 18. The top tool 16 is also floated coupled to the top tool
 table 38 to realize accurate positioning relative to the bottom tool. Of
 course, a greater or lesser number of shorter guide pillars 60 may be used
 within the confines of the invention.
 The top tool lever 46 is a generally A-shaped platform with a wide front
 portion and a narrower rear portion. The top tool table 38 and top tool
 lever 46 are interconnected at the front portions thereof by a lower and
 an upper pair of joint blocks 62 and 64 with pivot bearings. The lower
 pair of joint blocks 62 is mounted to an upper surface of the top tool
 table 38. The upper pair of joint blocks 64 is mounted to a lower surface
 of the top tool lever 46 by a pair of pivot joints 66. The pair of pivot
 joints 66, with radial bearings, substantially prevents friction on the
 longer guide pillars 40 when the top tool table 38 is moved on the Z-axis
 by rotation of the top tool lever 46.
 The top tool lever 46 extends rearwardly to a position outboard and
 rearwardly of the upstanding elongated rear portion 32 of the base block
 28. The rear end of the top tool lever 46 is pivotally connected to an
 upper end of an H-beam shaped rear push rod 68 (FIG. 12) that forms part
 of the latch assembly 22. The rear push rod 68 extends downwardly from the
 rear end of the top tool lever 46.
 The latch assembly 22 further includes an air cylinder 70 with an upper and
 a lower air inlet 72 and 74. The air cylinder 70 is outboard of and
 substantially parallel with the rear push rod 68. The air cylinder 70 also
 includes a retractable piston rod 16 therein, the lower end thereof
 connected to a latch 78. The latch 78 includes an upper and lower clevis
 80 and 82 pivotally interconnected to opposite ends of a push arm back 84.
 A pair of retraction springs 86 extends on opposite sides of the rear push
 rod 68 at a position proximate the lower end of the air cylinder 70 to an
 upper end of a curvewheel lever 88. Each of the retraction springs 86 is
 mounted against opposite sides of the rear push rod 68. The bracket 90 for
 the air cylinder 70 is also mounted against the rear push rod 68.
 The at least one press 12 is driven by the drive unit 20. Since the force
 to process the semiconductor chips exists for each tool at a different
 press moment, the drive unit 20 needs only the force for the heaviest
 process (usually the Dambar cut). The drive unit 20 includes a motor (not
 shown) coupled to a main shaft 92. The main shaft 92 is supported by a
 pair of bearings (not shown) and, in the preferred embodiment, carries up
 to six cam discs 94, each of which may be associated with a press 12. See,
 for example, FIG. 1 where a part of the main shaft is shown carrying three
 cam discs, two of which are associated with a press. Of course, a greater
 or lesser number of cam discs and associated cam discs are within the
 scope of this invention. A curvewheel 96 is resiliently urged by a
 compression spring 98 to follow the associated cam disc 94. The curvewheel
 96 rotates the curvewheel lever 88 which causes substantially vertical
 movement of the lower clevis 82.
 The cam discs 94 are the same, each including a key way (not shown) that
 fits with a key slot (not shown) in the main shaft 92. Asynchronization
 between the presses is achieved by varying the rotational position of the
 cam discs 94 relative to one another on the main shaft 92 by milling the
 key slots out of line along the longitudinal axis of the main shaft. The
 position of the key slots in the main shaft determines the rotational
 displacement of the cam discs relative to each other such that some tools
 are processing leadframe strips earlier than the other presses within a
 press cycle (See FIG. 8), i.e. the position of the cam disc on the main
 shaft determines whether the respective cam disc is in tool down or tool
 up position.
 The presses 12 follow the total curve of the cam disc 94 but the remaining
 stroke after the top tool 16 has reached the leadframe strip 24 (leadframe
 level =0 in FIG. 8) is variable in tool speed. The height of the top tool
 determines which part of the cam disc 94 is used as the starting point for
 processing the leadframe strip 24. The same cam disc 94 can be used for
 several different types of tools. As illustrated in FIG. 8, the flat part
 of the curve 100 is for the bending tool and the steep part of the curve
 102 is for the cutting tool.
 When the press 12 is in processing mode and the motor (not shown) is
 driven, the main shaft 92 will rotate in a clockwise direction as viewed
 in FIG. 1 causing the cam discs 94 to likewise rotate and the curvewheel
 96 to follow the cam disc 94. The curvewheel 96 rotates the curvewheel
 lever 88 which causes substantially vertical movement of the lower clevis
 82 causing the presses 12 to open and close in a desired sequence. In
 processing mode, the upper and lower devises 80 and 82 are vertically
 aligned with the push arm back 84 and the piston rod 76 is retracted into
 the air cylinder 70. The air cylinder 70 and the rear push rod 68 are also
 substantially vertically aligned or upright. The pair of retraction
 springs 86 maintains the latch assembly 22 in this processing
 configuration. Therefore, in the processing mode, the latch assembly 22 is
 like a "rigid" beam (See FIG. 11). The top tool lever 46 will move between
 a generally horizontal position and a slightly rotated position to
 vertically move the top tool table 38 while maintaining a substantially
 parallel relationship with the bottom tool table 36. Movement of the top
 tool table 38 causes movement of the top tool 16.
 The asynchronism is done between adjacent cam discs 94, so alternating top
 tools still operate together. With asynchronous movement of the tools
 rather than simultaneous movement thereof, there will not be two tools on
 the same leadframe strip 24 at the same time, which would pull the
 leadframe strip 24 prohibiting centering thereof and thus causing damage
 thereto. By phase displacing the moving of the top tools, the distance
 between adjacent tools can also be decreased, thus decreasing the length
 of the processing line. For example, FIGS. 1 and 2 show an exemplary two
 presses coupled to odd-numbered cam discs #1 and #3. Of course, in FIG. 1,
 it is also possible to place presses at cam discs #1 and #2, #2 and #3, or
 at #1, #2, and #3. If the distance between cam discs is 125 mm, the phase
 displacement between cam discs #1 and #3 may be zero. Cam discs two and
 four are phase displaced relative to cam discs one and three.
 In order to put a press 12 into the non-processing position, the latch
 assembly 22 of that press is activated by forcing air through the upper
 inlet 72 of the air cylinder 70. The air forces extension of the piston
 rod 76 from the air cylinder 70 rotating the latch assembly 22 downwardly
 and rearwardly to a collapsed position with the lower end of the rear push
 rod 68 and the air cylinder 70 becoming disposed at an outward angle to
 the rest of the press (See FIG. 11). As the latch assembly 22 collapses,
 the top tool lever 46 rotates quickly lifting the top tool table 38 and
 top tool 16 out of the way. The guide pillars 40 guide the top tool table
 38 via the caged ball bearing assembly 42 and bearing raceway 44 along the
 guide pillars 40 fixed in the bottom tool table 36. A shock absorber 104
 (FIG. 10) mounted against the base block 28 above the top tool table 38
 substantially prevents shock caused by the quick lifting movement and also
 serves as a bumper or upper end-position for the top tool table 38. The
 pair of retraction springs 86 maintains the latch assembly 22 in the
 collapsed position.
 Activating the latch assembly 22 quickly increases the tool-receiving space
 14 from about 15 mm up to about 60 mm by rotating the top tool lever 46 to
 lift the top tool table 38 and top tool 16 away from the leadframe strip
 process area. Accordingly, the latch assembly is often referred to as a
 "quick-lift assembly". The latch assembly 22 may be activated manually or
 automatically, for example, by sensor (not shown) or vision camera.
 For processing, the stroke must be as small as possible to overcome mass
 inertia forces. However, the quick-lift assembly 22 permits a larger
 tool-receiving space 14 to be created for visual inspection and cleaning
 of the tools i.e. a larger tool-receiving space makes the tools more
 accessible for tool exchange, repair, maintenance, etc. The cam discs 94
 determine the top tool stroke (15 mm) itself--the quick-lift assembly 22
 determines on what level this stroke takes place.
 In addition, the quick-lift assembly 22 permits processing of a leadframe
 strip 24 by an adjacent press even though an affected press may be in its
 tool up or non-processing position due to one of the semiconductor chips
 26 being defective. More specifically, if the defective semiconductor chip
 or chips 26 on a leadframe strip 24 is in a press, that press 12 may be
 placed in a non-processing position whereas the semiconductor chips in the
 other presses are normally processed. The affected press may be returned
 to processing position for further semiconductor chips following repair,
 for example, of the affected press. This is possible as each press 12 has
 a latch assembly 22 and each latch assembly is controllable and activated
 online during running without slowing down the system.
 Once the repair, for example, has been completed, the air is forced through
 the lower inlet 74 returning the quick-lift assembly 22 to its
 substantially vertically aligned form causing the press 12 to return to
 its processing configuration.
 Although a particular embodiment of the invention has been described in
 detail for purposes of illustration, various modifications may be made
 without departing from the spirit and scope of the invention. Accordingly,
 the invention is not to be limited, except as by the appended claims.