GB2617372A

GB2617372A - ESD tooling

Info

Publication number: GB2617372A
Application number: GB2205054.6A
Authority: GB
Inventors: Edmondson Glenn; Thomas Luke Walker William
Original assignee: ASM Assembly Systems Singapore Pte Ltd
Current assignee: ASMPT SMT Singapore Pte Ltd
Priority date: 2022-04-06
Filing date: 2022-04-06
Publication date: 2023-10-11
Also published as: GB202205054D0; CN116890513A; JP2023154422A; KR20230143930A; TW202341852A

Abstract

An electrostatic discharge protection tool for reducing electrostatic charge present on a workpiece, such as a PCB, comprises a movable conductive contact tip 13 (3 fig 2) for grounding a charged workpiece (W fig 2). The tip 13 is fixed to a movable head 12 (2 fig 2)located in a body 14 (4 fig 3) to extend and retract therefrom, and biased, preferably by a spring 15 between the head and body, towards the extended position. The tool provides an at least partially conductive path is formed between the tip of the and the body of the tool, preferably comprising a resistance 16, 17 (8 fig 2) to dissipate static charge. The tool may be located in a hole in a table of a PCB printer which can use other support pins. Figures 3a-b show an embodiment where resistances are provide in the electrical path between the head 12 and body 14 and ground 21, where the resistance can vary according to the head position due to the resistor network 16 and contact 20 on the head. Figure 5 shows alternative dissipating materials such as foams 47 (57,68) and figure 6-8 show addition of a contact 58, 70 directly to ground at the most retracted position.

Description

ESD Tooling This invention relates to an electrostatic discharge protection tool, a tooling block, a printing machine and a method of protecting a workpiece from electrostatic discharge.

Background and Prior Art

Industrial screen-printing machines typically apply a conductive print medium, such as solder paste, silver paste or conductive ink, onto a planar workpiece, such as a circuit board, by applying the conductive print medium through a pattern of apertures in a thin planar layer or mask, such as a stencil (which is a patterned solid material such as stainless steel) or a screen which is a mesh material coated with emulsion. The present invention is equally applicable to both screen and stencil printing, and for convenience the term "stencil" will be used to refer to any such patterned mask throughout the remainder of this document. The print medium is applied using an angled blade or squeegee, while the workpiece is clamped into a stationary printing position. The same machines may also be used to print certain nonconductive media, such as glue or other adhesive, onto workpieces. Following printing, the squeegee is lifted from the upper surface of the stencil, the stencil is separated from the printed workpiece, and the printed workpiece is unclamped.

Following such a printing operation within a printing machine, the printed workpiece may be transported to other processing modules within a production line. In particular, a printed workpiece may be transported to a placement machine which may place electrical or electronic components onto the workpiece.

To ensure high quality printing, it is necessary to support the workpiece so that the surface to be printed is parallel to the printing screen, generally horizontal, with the workpiece support being capable of withstanding the pressure placed upon it during the printing operation, especially by the downward pressure applied by the squeegee, while maintaining the correct alignment of the workpiece.

It is similarly necessary to provide suitable support for workpieces during placement operations, although the downward pressure exerted on a workpiece during a placement operation is generally far lower than that exerted during a printing operation.

The simplest type of support is to use a flat surface or platen on which a workpiece may be placed. However, there are many circumstances where this type of arrangement is not possible, in particular where the underside of a workpiece has previously been printed and equipped with components (for example during a previous placement operation), and this underside needs to be supported during a printing or placement operation applied to the topside of the workpiece. The presence of components on the underside of the workpiece means that the workpiece will not be flat, and also the components are liable to damage if they are "squashed" during a printing or placement operation. To this end, specialist support solutions, known as "tooling", are used.

There are currently two common tooling options for providing support for a printed circuit board (PCB) during printing and placement operations: 1) Dedicated tooling blocks -these are blocks of bulk material whose upper surface is caused, for example by machining, to have a three-dimensional profile designed to accommodate a specific PCB placed thereon. The tooling blocks may conveniently be located on a flat, underlying support plate or "tooling table".

2) Tooling pins -these are thin columns which are positioned to contact the board in use, avoiding contact with any components (or other delicate or critical regions) on the underside. The pins are usually magnetic, i.e. they include either a permanent or an electropermanent magnet within them, to non-permanently attach the pins to a tooling table, which may conveniently be made from a magnetically permeable material such as steel. By way of example, ASM currently uses simple, low-cost, moulded plastics tooling pins with a single Neodymium permanent magnet in the base of each pin. Within printing machines, tooling pins are usually manually placed on the tooling table (although auto-place systems are starting to be introduced), while placement machines, such as those produced by ASM, may provide both manual placing and auto-place options. With a manual system it is challenging and time consuming for the operator to place the pins consistently and with the required accuracy.

Auto-place systems may save time and reduce defects by placing pins accurately. An auto-place system typically uses a "pin picker" device operable to engage with a pin, the pin being located either on the tooling table or in a storage magazine, from above. The pin picker may then lift the pin, move it laterally into the desired position, then lower it onto the tooling table.

An example of such an auto-place system is schematically shown in FIG. 1. This auto-place system uses a "pin-picker" 102, a device operable to engage with one or more tooling pins 101A, 101B at a time from above, individual tooling pins 101A, 101B being located either on a support surface 123 of a tooling table or in a storage magazine 110. The pin-picker 102 may be movable in the vertical or "Z" direction to engage with and then lift a tooling pin 101A, 101B, and movable in orthogonal "X" and "Y" directions to move the tooling pin laterally into the desired position. The pin-picker 102 may then lower the tooling pin onto the support surface 123 of the tooling table, to which it is magnetically attracted. As shown, the pin-picker 102 is movable in the Z direction with respect to a supporting gantry 120 from which it is suspended, and movable along the gantry 120 in the X direction. Y movement is provided by moving the gantry 120 in the Y direction. Although not shown in FIG. 1, the gantry 120 may be supported within a processing module such as a printing or placement machine. The placed locations of the tooling pins 101A, 101B on the support surface 123 are manually or automatically chosen in dependence of a workpiece 130 to be subsequently supported. The workpiece 130 shown comprises a substrate 131, such as a board or semiconductor wafer, which in this example has a number of features on the underside which hinder support of the workpiece 130. These features may include components 132, vias 133 or the like, as will be understood by those skilled in the art. The location and type of tooling pins 101A, 101B placed on the support surface 123 will depend on the location of such features. In the example shown, tooling pins 101A, which are relatively wide, are used where space between features permits, while relatively thin tooling pins 101B are used where the space between features is small.

Typically, once the workpiece has been transported into a printing or placement machine, the tooling and overlying workpiece are brought into supporting contact by raising the tooling, for example by lifting the tooling table, until the tooling is brought into contact with the workpiece.

Electronic components present on a workpiece during a printing or placement operation are susceptible to damage through electrostatic discharge ("[SD"), which could occur if the workpiece becomes electrostatically charged. There are various opportunities for a workpiece to become charged, and as an example it has been found that a particularly high risk of charging occurs during a printing process, due to the contact and separation between: -the squeegee and stencil, - the stencil and the workpiece, and - the workpiece and clamps which hold it in the printing position.

While the tooling may provide [SD protection (e.g. tooling pins are usually made of dissipative material to dissipate electrostatic charge build-up), this is not always reliable. For example, there may be imperfect contact between the pins and workpiece at any stage in which the squeegee is not applying a downward force to the overlying stencil.

The present invention seeks to overcome this problem, and provide reliable protection from [SD during a processing operation, such as printing or placement.

In accordance with the present invention this aim is achieved by providing a variable height [SD-protection component associated with the tooling, which can ensure contact with the workpiece over a range of distances. In addition, an optimal location for the [SD-protection component is determined through analysis of the Gerber data associated with the workpiece, and the component may be placed in the determined location.

Summary of the Invention

In accordance with a first aspect of the present invention there is provided an electrostatic discharge protection tool for reducing electrostatic charge present on a workpiece within a workpiece processing module, comprising: a body, a head, a tip located at a distal end of the head, the tip being at least partially conductive, the head being moveable with respect to the body between an extended position in which the tip is at a maximum distance from the body and a retracted position in which the tip is at a minimum distance from the body, biasing means for biasing the head to the extended position, and an at least partially conductive path formed between the tip and the body, for grounding a charged workpiece in contact with the tip.

In accordance with a second aspect of the present invention there is provided a tooling block for supporting a workpiece during a processing operation, comprising the electrostatic discharge protection tool of the first aspect.

In accordance with a third aspect of the present invention there is provided a printing machine comprising the electrostatic discharge protection tool of the first aspect.

In accordance with a fourth aspect of the present invention there is provided a method of protecting a workpiece from electrostatic discharge, comprising the steps of: i) locating tooling on a tooling table of a workpiece processing module to support the workpiece during a processing operation, the tooling including an electrostatic discharge protection tool in accordance with the first aspect, ii) transporting the workpiece to a processing position overlying the tooling, and iii) relatively moving the workpiece and tooling table together to bring the tooling into supporting contact with the workpiece and the tip of the electrostatic discharge protection tool into contact with the workpiece, so as to ground the workpiece via the at least partially conductive path.

Other specific aspects and features of the present invention are set out in the accompanying claims.

Brief Description of the Drawings

The invention will now be described with reference to the accompanying drawings (not to scale), in which: FIG. 1 schematically shows, in sectional view, a known auto-place system; FIG. 2 schematically shows, in sectional view, an embodiment of the present invention including an electrostatic discharge protection tool fitted within a tooling block; FIGs. 3A and 3B schematically show, in extended and retracted positions respectively, an electrostatic discharge protection tool in section; FIG. 4 schematically shows an electrostatic discharge protection tool incorporating a digital potentiometer; FIG. 5 schematically shows, in section, an alternative embodiment of an electrostatic discharge protection tool; FIG. 6 schematically shows, in section, a further alternative embodiment of an electrostatic discharge protection tool; FIGs. 7 and 8 schematically show, in section, an alternative embodiment in extended and retracted positions respectively; and FIG. 9 schematically shows, in section, an electrostatic discharge protection tool formed as a free-standing column.

Detailed Description of the Preferred Embodiments of the Invention An embodiment of the present invention is shown in FIG. 2, which schematically shows, in sectional view, an electrostatic discharge protection tool 1 fitted within a tooling block 7. The tooling block 7 is located on a tooling table (not shown) for vertical movement into and out of engagement with an overlying workpiece W. In more detail, the electrostatic discharge protection tool 1 comprises a head 2 having a tip 3 located at a distal (i.e. top) end of the head 2. The head 2 is connected to a body 4 so as to be moveable with respect thereto. As shown, the head 2 is moveable along the vertical or Z axis relative to the body 4, which in use remains stationary with respect to the tooling block 7. The head 2 is moveable with respect to the body 4 between an extended position (as shown in FIG. 2) in which the tip 3 is at a maximum distance from the body 4 and a retracted position (not shown) in which the tip 3 is at a minimum distance from the body 4. This arrangement may be effected, by way of example only, by provided a cylindrical, vertically extending passage (not shown) in the body 4 and locating the head 2 within the passage for sliding vertical movement therethrough, the sides of the passage constraining lateral movement of the head 2. Vertical movement of the head 2 beyond either the retracted or extended positions may be prevented by at least partially closing the distal ends of the passage, for example the lower end of the passage may be closed completely. The upper end of the passage must however remain partially open, so that a portion of the head 2 including the tip 3 may pass through. Advantageously, the head 2 may comprise a collar or shoulder portion at its lower end of greater lateral extent that the upper portion of the head 2, which collar prevents egress of the head 2 through the opening at the upper end of the passage. Located within the electrostatic discharge protection tool 1 is a biasing means (not shown) for biasing the head 2 to the extended position. The biasing means may for example comprise a compression spring or compressible foam material.

The tip 3 is at least partially conductive, and may be formed from a metallic material for example. The tip 3 thereby forms part of an at least partially conductive path formed between the tip 3 and the body 4 for grounding a charged workpiece W when in contact with the tip 3. As schematically shown in FIG. 2, the body 4 is connected to ground at an earth connection 6 at the lowest extremity of the electrostatic discharge protection tool 1, via a resistance 8, chosen to safely allow a rapid discharge if a charged workpiece contacts the tip 3. A resistance of around 1 MO has been found to be suitable for many workpieces, although this will depend on the particular application. The electrostatic discharge protection tool 1 is located within an opening 9 formed in the tooling block 7 and electrically isolated therefrom by an insulating collar 5 or sleeve formed from an insulative material. Typically, the tooling block 7 may comprise a bulk material, and the opening 9 is formed in the bulk material. It can be seen from FIG. 2 that in the extended position, the tip 3 projects past the upper surface of the tooling block 7, so that in use the workpiece W will contact the tip 3 before the tooling block 7.

In use: -the tooling block 7 is located on a tooling table (not shown) of a workpiece processing module to support the workpiece W during a processing operation, the tooling block including the electrostatic discharge protection tool 1; -The workpiece W, which may be highly electrostatically charged, is transported to a processing position overlying the tooling block 7, into the position shown in FIG. 2, and -The workpiece W and tooling table are moved together, in this case by lifting the tooling table. The tip 3 of the electrostatic discharge protection tool is thereby brought into contact with the workpiece W, so as to ground the workpiece W via the at least partially conductive path. Subsequently, by further lifting of the tooling table, the head is pushed down towards the retracted position against the biasing means, while remaining in contact with the underside of the workpiece W, until the tooling block 7 is brought into supporting contact with the workpiece W. When the workpiece 7 is fully supported on the tooling block 7, the processing operation may be performed.

It is beneficial for the tip 3 of the electrostatic discharge tool 1 to contact a conductive area of the underside of the workpiece W, such as a conductive pad or track previously printed onto the workpiece W. Therefore, the method outlined above preferably comprises an initial step of determining a location, within the horizontal plane, for the electrostatic discharge protection tool 1 such that it underlies a conductive region of the workpiece W. A preferred way of doing this is to analyse the Gerber data associated with the workpiece W, which Gerber data accurately provides location information of conductive regions of the workpiece W. The above-described embodiment provides a robust methodology for protecting the workpiece W from electrostatic discharge. In alternative embodiments, a more sophisticated electrostatic discharge protection tool may be provided in which the resistance of the at least partially conductive path varies dependent on the distance between the tip and the body, to optimise the discharge through the tool.

FIGs. 3A and 3B schematically show, in extended and retracted positions respectively, an electrostatic discharge protection tool 11 in section. The electrostatic discharge protection tool 11 again comprises a head 12 with a tip 13, the head being relatively moveable with respect to a body 14 between an extended position shown in FIG. 3A and a retracted position shown in FIG. 3B. The head 12 is biased to the extended position by a biasing means in the form of a compression spring 15. The body 14 includes a resistor network 16 having a plurality of resistors 17 of different respective resistances. These are arranged such that the at least partially conductive path comprises a first resistor of the plurality of resistors when the distance between the tip 13 and the body 14 is a first distance, and the at least partially conductive path comprises a second resistor of the plurality of resistors when the distance between the tip 13 and the body 14 is a second distance, as will be described below. The head 12 includes an electrical contact 20 at its lowest extent, which is configured to electrically contact a single resistor 17 of the plurality of resistors at any point along its range of travel between the extended position and the retracted position. In the extended position shown in FIG. 3A, the electrical contact 20 makes electrical contact with a first resistor 18, while in the retracted position shown in FIG. 3B, the electrical contact 20 makes electrical contact with a second resistor 19, the first and second resistors 19, 20 having different resistances. At intermediate points along the travel between the extended and retracted positions, the electrical contact 20 makes electrical contact with other resistors of the plurality of resistors.

The resistor network 16 is connected to ground at an earth connection 21. In this way the discharge of electrostatic charge on a workpiece coming into contact with the tip 13 can be controlled, and thereby provide a slower discharge for a charged workpiece.

FIG. 4 schematically shows an alternative embodiment of an electrostatic discharge protection tool 31. In this embodiment, the resistance of the at least partially conductive path is varied using a variable resistor, in this case a digital potentiometer 32 connected to the lower end of the body of the electrostatic discharge protection tool. The digital potentiometer 32 is controlled with a controller 33, such as a processor or the like running or controlled by suitable software or hardware. Such a system could be used to provide a 1M12 to 00 transition when a workpiece is clamped, to provide a relatively slow discharge, and negligible impedance, such as 00, when the workpiece is unclamped, to give a direct path to ground to transfer any static created in the printing process.

FIG. 5 schematically shows, in section, an alternative embodiment of an electrostatic discharge protection tool 41 in the extended position. In this embodiment, [SD protection is provided by using dissipative material in the at least partially conductive path, and, similarly to the embodiment shown in FIGs. 3A and 3B, the resistance of the at least partially conductive path varies dependent on the distance between the tip and the body, to optimise the discharge through the tool. The electrostatic discharge protection tool 41 again comprises a head 42 with a tip 43, the head 42 being relatively moveable with respect to a body 44 between the extended position shown and a retracted position (not shown). The head 42 is biased to the extended position by a biasing means in the form of a compression spring 45.

The body is retained in an opening of a tooling block (not shown) via an insulating collar 48. The body 44 includes a plurality of dissipative materials 47, such as dissipative foam materials for example, of different respective resistances., and more for example be formed as collars or annuli surrounding the path of travel of the head 42. These are arranged such that the at least partially conductive path comprises a first dissipative material of the plurality of dissipative materials when the distance between the tip 43 and the body 44 is a first distance, and the at least partially conductive path comprises a second dissipative material of the plurality of dissipative materials when the distance between the tip 43 and the body 44 is a second distance, as will be described below. The head 42 includes an electrical contact 46 at its lowest extent, which is configured to electrically contact a single dissipative material 47 of the plurality of dissipative materials at any point along its range of travel between the extended position and the retracted position. In the extended position shown for example, the electrical contact 46 is in contact with the uppermost dissipative material 47. Along its travel between the extended and retracted positions, the electrical contact 46 makes electrical contact with other dissipative materials of the plurality of dissipative materials. In this way the discharge of electrostatic charge on a workpiece coming into contact with the tip 43 can be controlled.

The embodiments shown in FIGs. 3 to 5 provide a varying resistance throughout the range of travel. In some advantageous embodiments of the present invention, this idea can be extended so that the ESD protection regime can be diverted between a conductive path and a dissipative path dependent on the extent of travel of the head between the extended and retracted positions.

FIG. 6 schematically shows, in section, such an embodiment. The electrostatic discharge protection tool 51 is very similar to the electrostatic discharge protection tool 41 of FIG. 5, including a plurality of dissipative materials 57 of different respective resistances, which are contacted sequentially by the electrical contact 56 throughout its range of travel. In addition, a conductive contact 58, of low electrical resistance, is provided near the lowest extent of the range of travel, arranged to contact the electrical contact 56 when in the retracted position. The conductive contact 58 is electrically connected to an earth connection 59, which is connected to ground.

FIGs. 7 and 8 schematically show an alternative embodiment in which the ESD protection regime can be diverted between a conductive path and a dissipative path dependent on the extent of travel of the head between the extended and retracted positions. FIG. 7 schematically shows, in section, an electrostatic discharge protection tool 61 in an extended position, while FIG. 8 shows the electrostatic discharge protection tool 61 in the retracted position. The electrostatic discharge protection tool 61 is again located within an opening in a tooling block 67. A head 62, having a tip 63, is moveably mounted in a body 64, and biased to an extended position by a biasing means in the form of a compression spring 65. The head 62 includes an electrical contact 66 which is configured to contact one of a plurality of dissipative materials 68 located within the body as the head 62 moves from the extended position towards the retracted position shown in FIG. 8. The arrangement of dissipative materials 68 and electrical contact 66 may be similar to that described above with reference to FIG. 5 and 6 for example. The head 62 includes a stem 69 which depends downwardly from the electrical contact 66 and is, similar to the tip 63, electrically conductive, so that a conductive path is formed between the tip 63 and the lowest part of the stem 69.

The stem 69 is slidably arranged within an aperture 71 formed in the base of the body 64. A conductive contact 70, in the form of a leaf spring, is provided at the base of the opening within the tooling block 67, arranged angled upwardly so as to contact the stem 69 when the head 62 approaches and enters the retracted position, as shown in FIG. 8. The conductive contact 70 is connected to ground, and thereby effective to earth a charged workpiece (not shown) that may be in contact with the tip 63.

The embodiments described above all use an electrostatic discharge protection tool which is embedded into a tooling block, and may be used as set out in detail with respect to the first embodiment, i.e. - the tooling block is located on a tooling table (not shown) of a workpiece processing module to support a workpiece W during a processing operation, the tooling block including the electrostatic discharge protection tool; - The workpiece W, which may be highly electrostatically charged, is transported to a processing position overlying the tooling block, and - The workpiece W and tooling table are moved together, for example by lifting the tooling table. The tip of the electrostatic discharge protection tool is thereby brought into contact with the workpiece W, so as to ground the workpiece W via the at least partially conductive path. Subsequently, by further lifting of the tooling table, the head is pushed down towards the retracted position against the biasing means, while remaining in contact with the underside of the workpiece W, until the tooling block is brought into supporting contact with the workpiece W. When the workpiece is fully supported on the tooling block, the processing operation may be performed.

Furthermore, with all of these embodiments, it is beneficial for the tip of the electrostatic discharge tool to contact a conductive area of the underside of the workpiece W, such as a conductive pad or track previously printed onto the workpiece W. Therefore, the method outlined above preferably comprises an initial step of determining a location, within the horizontal plane, for the electrostatic discharge protection tool such that it underlies a conductive region of the workpiece W. A preferred way of doing this is to analyse the Gerber data associated with the workpiece W, which Gerber data accurately provides location information of conductive regions of the workpiece W. As noted previously, other types of tooling are commonly used, and in particular tooling pins are common. The present invention is equally applicable to such systems, and the electrostatic discharge protection tool may comprise a free-standing column, optionally adapted to provide support for the workpiece during the processing operation, similar to a standard tooling pin. Here, the term "free-standing column" is used to mean an item of elongate form, having a primary axis along its length, which may be placed onto a flat, horizontal surface such that the primary axis extends vertically, without the item being supported other than by the flat, horizontal surface. Such an electrostatic discharge protection tool may also be adapted to be placed by a smart pin placement system.

FIG. 9 schematically shows an electrostatic discharge protection tool 81 formed as a free-standing column, and is usable as a tooling pin. The electrostatic discharge protection tool 81 comprises a head 82 with a tip 83 at the upper end thereof, the head 82 being relatively moveable with respect to a body 84. Biasing means (not shown), such as a compression spring biases the tip 83 away from the body 84 into an extended position shown. The top of the body is designated as 87. An at least partially conductive path is formed between the tip 83 and the lowest end of the body 84, which can ground a charged workpiece (not shown) in contact with the tip 83, with the grounding being effected through the tooling table 85 on which the electrostatic discharge protection tool 81 is placed. Internally therefore, the electrostatic discharge protection tool 81 may be similar to the electrostatic discharge protection tool 1 shown in FIG. 2. The electrostatic discharge protection tool 81 includes engagement means 86, here taking the form of detents, in body 84. The engagement means 86 is provided to allow engagement with a latch 89 of a pin-picker 88 of a pin placement mechanism.

During use, the head 82 will be forced towards its retracted position, in which the tip 83 will be at or slightly higher than the top of the body 87. The top of the body 87 may therefore provide support for the workpiece similarly to a standard tooling pin.

In alternative embodiments (not shown), the resistance of the at least partially conductive path may vary dependent on the distance between the tip and the body, similarly to the electrostatic discharge protection tools 11, 31, 41, 51, 61 previously described.

An advantage of such a tooling pin-style arrangement is that there is greater flexibility in placement of the electrostatic discharge protection tool 81. Advantageously, a location is determined, within the horizontal plane, for the electrostatic discharge protection tool 81 such that it underlies a conductive region of a workpiece in use. A preferred way of doing this is to analyse the Gerber data associated with the workpiece, which Gerber data accurately provides location information of conductive regions of the workpiece. The electrostatic discharge protection tool 81 may then be positioned on the tooling table 85, advantageously by using a pin-picker 88 of a pin-placement mechanism (although manual placement by an operator is also possible), at the determined location. Once any other required tooling pins are also placed, a workpiece may then be transported to a processing position overlying the placed tooling pins and electrostatic discharge protection tool 81. The workpiece and tooling table 85 are moved closer together, for example by lifting the tooling table 85. The tip of the electrostatic discharge protection tool 81 is thereby brought into contact with the workpiece, so as to ground the workpiece via the at least partially conductive path. Subsequently, by further lifting of the tooling table 85, the head 82 is pushed down towards the retracted position against the biasing means, while remaining in contact with the underside of the workpiece, until the tooling pins are brought into supporting contact with the workpiece. In this position the electrostatic discharge protection tool 81 may also provide support to the workpiece. When the workpiece is fully supported on the tooling pins, the processing operation may be performed. Following processing, the tooling pins and electrostatic discharge protection tool 81 may remain in place, be repositioned as required, or returned to a magazine (not shown) for future use.

The above-described embodiments are exemplary only, and other possibilities and alternatives within the scope of the invention will be apparent to those skilled in the art.

Reference numerals used: 1, 11, 31, 41, 51, 61, 81 -Electrostatic discharge protection tool 2, 12, 42, 62, 82 -Head 3, 13, 43, 63, 83 -Tip 4, 14,44, 64, 84 -Body 5,48 -Insulating collar 6, 21, 59 -Earth connection 7, 67-Tooling block 8-Resistance 9-Opening 15, 45, 65 -Compression spring 16 -Resistor network 17 -Resistors 18 -First resistor 19 -Second resistor 20, 46, 56, 66 -Electrical contact 32 -Digital potentiometer 33 -Controller 47, 57, 68-Dissipative material 58, 70-Conductive contact 69 -Stem 71 -Aperture

-Tooling table

86 -Engagement means 87 -Top of body 88-Pin picker 89 -Latch 101A, 101B -Tooling pins 102 -Pin picker 110-Storage magazine 120-Gantry 130-Workpiece 131 -Substrate 132 -Components 133 -Via W -Workpiece

Claims

Claims 1. An electrostatic discharge protection tool for reducing electrostatic charge present on a workpiece within a workpiece processing module, comprising: a body, a head, a tip located at a distal end of the head, the tip being at least partially conductive, the head being moveable with respect to the body between an extended position in which the tip is at a maximum distance from the body and a retracted position in which the tip is at a minimum distance from the body, biasing means for biasing the head to the extended position, and an at least partially conductive path formed between the tip and the body, for grounding a charged workpiece in contact with the tip.
2. The electrostatic discharge protection tool of claim 1, wherein the resistance of the at least partially conductive path varies dependent on the distance between the tip and the body.
3. The electrostatic discharge protection tool of claim 2, comprising a resistor network having a plurality of resistors of different respective resistances, arranged such that the at least partially conductive path comprises a first resistor of the plurality of resistors when the distance between the tip and the body is a first distance, and the at least partially conductive path comprises a second resistor of the plurality of resistors when the distance between the tip and the body is a second distance.
4. The electrostatic discharge protection tool of claim 2, wherein the at least partially conductive path comprises a variable resistor, optionally an electrically-controllable potentiometer.
5. The electrostatic discharge protection tool of claim 2, comprising a plurality of dissipative materials of different of different resistances, arranged such that the at least partially conductive path comprises a first dissipative material of the plurality of dissipative materials when the distance between the tip and the body is a first distance, and the at least partially conductive path comprises a second dissipative material of the plurality of dissipative materials when the distance between the tip and the body is a second distance.
6. The electrostatic discharge protection tool of any preceding claim, comprising a conductive contact arranged to constitute part of the at least partially conductive path when the head is in the retracted position, but not when the head is in the extended position.
7. The electrostatic discharge protection tool of any preceding claim, comprising a free-standing column, optionally adapted to provide support for the workpiece during the processing operation.
8. The electrostatic discharge protection tool of claim 7, comprising engagement means for engagement with a pin placement mechanism of the workpiece processing module.
9. A tooling block for supporting a workpiece during a processing operation, comprising the electrostatic discharge protection tool of any of claims 1 to 6.
10. The tooling block of claim 9, comprising a bulk material with the electrostatic discharge protection tool located within an opening formed in the bulk material.
11. The tooling block of claim 10, comprising a dissipative material disposed between the tip and the tooling block, so that the at least partially conductive path is arranged to ground via the bulk material.
12. A printing machine comprising the electrostatic discharge protection tool of any of claims 1 to 8.
13. The printing machine of claim 12, comprising a tooling table for supporting tooling thereon, the electrostatic discharge protection tool being located on the tooling table.
14. A method of protecting a workpiece from electrostatic discharge, comprising the steps of: i) locating tooling on a tooling table of a workpiece processing module to support the workpiece during a processing operation, the tooling including an electrostatic discharge protection tool in accordance with any of claims 1 to 8, ii) transporting the workpiece to a processing position overlying the tooling, and iii) relatively moving the workpiece and tooling table together to bring the tooling into supporting contact with the workpiece and the tip of the electrostatic discharge protection tool into contact with the workpiece, so as to ground the workpiece via the at least partially conductive path.
15. The method of claim 14, comprising the initial step of determining a location for the electrostatic discharge protection tool such that it underlies a conductive region of the workpiece.
16. The method of claim 15, wherein the step of determining the location comprises analysing Gerber data associated with the workpiece.
17. The method of any of claims 14 to 16, wherein the tooling comprises a tooling block.
18. The method of any of claims 14 to 16, wherein the tooling comprises a plurality of tooling pins.
19. The method of claim 18, wherein step i) comprises using a pin placement mechanism of the processing module to move the tooling pins and electrostatic discharge protection tool.
20. The method of any of claims 14 to 19, wherein the processing module comprises a printing machine.