Patent Publication Number: US-2016238415-A1

Title: Method of manufacturing an electronic component

Description:
The present invention relates to a method of manufacturing an electrical component, in particular a printed circuit board, such as a printed circuit board for a measurement device, such as a position measurement encoder apparatus. 
     Position measurement encoders are known wherein the scale comprises a series of generally periodic features which the readhead can read to determine and measure relative motion. Various types of position measurement encoder exist, including incremental encoders and absolute encoders. Also, position measurement encoders can utilise various means of reading a scale, including optical, magnetic, capacitive and/or inductive (a position measurement encoder can utilise more than one such means for reading a scale). 
     Typically, optical incremental encoders operate by the scale (and often one or more diffraction gratings within the readhead) interacting with light from a source within the readhead to generate at a detector a resultant field (e.g. modulated spot(s) or interference fringes) which changes with relative movement of the scale and readhead. Often, but not necessarily, one or more reference marks are provided (e.g. embedded within or next to the series of features) such that relative position can be determined with respect to known reference positions defined by the reference marks. An example of an optical incremental encoder is described in WO2005/124282. 
     Typically, absolute encoders operate by the scale defining unique patterns (e.g. codes) which can be read by a readhead. Examples of absolute encoders are described in WO2002/084223 and WO2010/049682. 
     It can be important when manufacturing electrical devices, such as encoders for example, to locate the position of one or more components that make up the electrical device precisely in order to achieve good functionality. 
     This application describes a method of manufacturing an electrical device in which an electrical connection is made to a component of the electrical device during said manufacture. 
     According to a first aspect of the invention there is provided a method of manufacturing an electronic device, for example a measurement device (e.g. a position measurement device), comprising at least one sensor, the method comprising: positioning at least one component of the electronic device using the output from the sensor. 
     Accordingly the output from the sensor can be used in the process of positioning the at least one component (e.g. used to help determine a preferred/optimum positioning of the at least one component). Using the output from the sensor to aid positioning the at least one component can improve the quality of the electronic device. It can aid preferred/optimum positioning of the component with respect to the rest of the electronic device, which can be useful in optimising the electronic device, for example in optimising the output from the sensor. For instance, in the case of a measurement device, it can help improve the accurate placement of the measurement device at a preferred or optimum position. 
     The electronic device can be measurement device, e.g. a metrological device, in particular a device used in the obtaining of dimensional measurements. The electronic device can comprise a readhead for a position measurement encoder apparatus. As will be understood, such a readhead can be configured to read a scale. The readhead could be a readhead for an incremental encoder apparatus (e.g. for reading an incremental scale comprising incremental position features) or a readhead for an absolute encoder apparatus (e.g. for reading an absolute scale comprising absolute position features). 
     The sensor can be a sensor configured to be used during operation of the electronic device. For instance, in the case of the electronic device being a measurement device, the sensor can be that which the measurement device is configured to use to obtain measurements during a measurement process. For example, in the case of a readhead for an encoder apparatus which is configured to detect a scale to determine relative motion between the scale and readhead, the sensor can be that which the readhead is configured to use to detect/read the scale. 
     Accordingly, the sensor can be suitable for reading a scale comprising a series of markings The output of the sensor can be configured for use in determining the relative position of the readhead and a scale. The method can comprise, placing a calibration artefact such that the sensor can detect the calibration artefact and positioning the at least one component (e.g. the sensor—see below) using output from the sensor (e.g. tweaking the relative location of the sensor and/or the at least one component using the output from the sensor). The calibration artefact could be a piece of scale. 
     The at least one component can comprise the at least one sensor. Accordingly, the method can comprise positioning the sensor using the output from the sensor. 
     The electronic device can be an optical electronic device, in particular an optical measurement device, for example an optical encoder device (e.g. in that it uses optics in its operation, e.g. electromagnetic radiation (EMR) in the infra-red to ultraviolet range). Accordingly, the sensor can be an optical sensor (also known as an electro-optical sensor). The sensor can comprise at least one photodetector, for example a plurality of photodetectors, for instance an array of photodetectors. As explained in more detail below, the sensor can comprise an array of photodetectors for detecting an interference fringe. The sensor can comprise two or more sets of interdigitated/interlaced photodetectors, each set configured to detect a different phase of an interference fringe. 
     The at least one component can comprise an optical component configured to interact with optical radiation before the optical radiation reaches the sensor. Hereinafter, optical radiation is referred to as “light”, and as will be understood comprises EMR in the infra-red to ultraviolet range. The optical component can comprise a lens. For example, the lens could be configured to focus light onto one or more spots on the sensor. Optionally, the lens could be used to produce an image of an object (e.g. a scale) on the sensor. The optical component can comprise a diffraction grating. The diffraction grating could be used to form a resultant field on the sensor which changes with movement of the electronic device relative to an external object (e.g. a scale). For example, the resultant field could comprise an interference fringe which changes/moves with relative movement of the electronic device and the object/scale. For example, the resultant field could comprise a light spot which modulates between relative dark and bright with relative movement of the electronic device and the object/scale. Examples of other types of optical component include (but not limited to) mirrors, prisms, zone plates (e.g. Fresnel zone plate), and beam splitters). 
     The method can comprise positioning at least one component of the electronic device with respect to at least one other component of the electronic device using the output from the sensor. The at least one component can comprise the at least one sensor or an optical component (e.g. an optical component for interacting with optical radiation before the light reaches the sensor). The at least one other component of the electronic device can comprise the other of the at least one sensor and the optical component (e.g. an optical component for interacting with optical radiation before the light reaches the sensor). 
     The output from the sensor can be used by an operator, i.e. a human operator, in order to aid positioning the at least one component. For instance, a device could provide a visual indication (e.g. display on a screen) of information (e.g. a graphical representation) which is dependent on the output and which the user can use to tweak the position of the at least one component. 
     The method can comprise a manufacturing apparatus comprising an actuator holding and moving the at least one component. The method can further comprise a processor device controlling the motion of the actuator so as to position the at least one component based on the output from the sensor. The method can comprise a processor device controlling the motion of the actuator so to tweak the position of the at least one component based on the output from the sensor. The method can comprise analysing the output from the sensor at at least one particular position and/or orientation of the at least one component. The method can further comprise adjusting the position of the at least one component based on (e.g. the result/outcome of) such analysis. The method can comprise monitoring the output from the sensor for a series of different test configurations. 
     The output can comprise a signal, for example an analogue or digital signal. The method can comprise using the raw signal output from the sensor. Optionally, the method comprises using a processed version of a signal output from the sensor. Optionally, software and/or electronics (e.g. a processor device) is configured to process the output from the sensor to provide data which can be used to determine how to position the at least one component. Such software and/or electronics (e.g. a processor device) can be provided as part of and/or separately to the measurement device. Accordingly, the decision on how to position the at least one component can be based on the direct output from the sensor, or on a signal/data obtained by processing the direct output from the sensor. In either case, as will be understood, the output from the sensor is used in the positioning of the at least one component. In other words, the positioning of the at least one component is dependent on the output from the sensor. 
     The manufacturing apparatus could communicate with the sensor wirelessly. The manufacturing apparatus can comprise at least one electrical connector for electrically connecting to the at least one component (e.g. the sensor) when it is held by the actuator. When the at least one component is not the sensor, but another electrical component, then it might be useful to provide an electrical connection, e.g. so as to supply power and/or so as to install and/or retrieve data). 
     As will be understood, the at least one electrical connector need not physically connect directly to the sensor. Rather, for example, the sensor could be mounted on another component (e.g. a printed circuit board (PCB)) and the at least one electrical connector can be configured to physically connect to a contact on the other component (e.g. on the PCB). 
     The actuator can comprise the at least one electrical connector. 
     The actuator can comprise at least one gripper, for example a plurality of grippers, for engaging the at least one component, in particular so as to facilitate the holding of the at least one component. In the case in which the at least one component is a PCB (e.g. a PCB on which the sensor is mounted), the at least one gripper can be biased laterally across the PCB. For example, the at least one gripper can be biased parallel to the plane of the PCB. The at least one gripper can be biased against a surface extending between the faces of the printed circuit. The at least one gripper can be biased against the peripheral edge of the PCB. 
     Said at least one gripper can comprise the above mentioned at least one electrical connector. Accordingly, in other words, at least one gripper can comprise one or more electrical connectors. As will be understood, the actuator could comprise at least one gripper which comprises at least one electrical connector and at least one gripper which does not comprise an electrical connector. 
     Optionally, at least one electrical connector is provided separately to the gripper (which could optionally itself comprise at least one electrical connector). In this case, optionally, the at least one gripper and at least one electrical connector are biased laterally across the PCB. For example, the at least one gripper and at least one electrical connector are biased parallel to the plane of the PCB. 
     The at least one gripper and at least one electrical contact can be biased against a surface extending between the faces of the PCB. The at least one gripper and at least one electrical connector can be biased against the peripheral edge of the PCB. 
     The peripheral edge of the PCB can comprises at least one recess in which the at least one gripper and/or at least one electrical connector are received. Accordingly, this can be such that they sit at least flushly with, and optionally within, the predominant outer perimeter defined by the PCB. 
     A plurality of electrical connectors can be provided for connecting to the at least one component (e.g. the at least one sensor). For example, one or more electrical connectors can be used to supply electrical power to the sensor (and optionally any other associated components). For example, one or more electrical connectors can be used to supply electrical power to a PCB on which the sensor is provided (and optionally any other associated components). For example, one or more electrical connectors can be used to facilitate communication with the sensor (and optionally any other associated components). For example, one or more electrical connectors can be used to facilitate communication with the sensor (and optionally any other associated components). 
     Data can be transferred between the printed circuit board and a processor device via the electrical connection. Data can be transferred to and/or from a memory device on the printed circuit board via the electrical connection. 
     As mentioned above, the sensor can be mounted on a PCB. The at least one gripper and at least one electrical connector can be biased against the PCB in the same direction. The at least one gripper and at least one electrical connector can be biased laterally across the PCB. The at least one gripper and at least one electrical connector can be biased against a surface extending between the planar faces of the PCB. The at least one gripper and at least one electrical connector can be biased against the peripheral edge of the PCB. 
     Optionally, the measurement device comprises a readhead for an encoder apparatus. The sensor can be suitable for reading a scale comprising a series of markings. The output from the sensor can be configured for use in determining the relative position of the readhead and a scale. The method can comprise placing a calibration artefact such that the sensor can detect the calibration artefact. The method can comprise tweaking the relative location of the sensor and/or at least one other (e.g. optical) component using the output from the sensor. 
     Accordingly, this application describes, a method of manufacture comprising a manufacturing apparatus comprising an actuator comprising at least one gripper picking up a printed circuit board (“PCB”) and locating it with respect to another component at preferred position, the apparatus comprising at least one electrical connector for electrically connecting to the PCB when it is picked up by the actuator, the at least one gripper and at least one electrical connector being biased against the PCB in the same dimension. 
     The at least one gripper can provide at least one electrical connector. Electrical power can be supplied to the printed circuit board via the electrical connection. 
     The PCB can comprise at least one sensor, the output of which is supplied to a processor via the at least one electrical connector. The processor can control the motion of the actuator, and hence the position of the PCB relative to the other component, based on the output from the least one sensor. The processor can control the position of the PCB with respect to a housing to which the printed circuit board is to be secured. The sensor can comprises a photodetector array, the housing can comprises a diffraction grating which interacts with electromagnetic radiation (“EMR”) to produce a resultant field on the sensor. The resultant field can be an interference fringe which moves with relative movement between the sensor and diffraction grating. The method can comprising placing a scale comprising a series of periodic markings defining an incremental scale track such that light interacts with the scale and the diffraction grating to produce the resultant field on the sensor. 
     The method can comprise releasing the PCB from the actuator. The method can comprise securing the PCB to the other component prior to releasing the actuator from the PCB. Releasing the PCB from the actuator can comprise releasing the bias of the at least one electrical connector against the PCB before releasing the bias of the at least one gripper against the PCB. 
     This application also describes, a method of manufacturing a sensor device (e.g. an encoder readhead), the sensor device comprising at least one sensor component (e.g. a photodiode), in which the method comprises reading data out from the sensor component during the manufacturing process and using said data to aid the manufacturing process. 
     According to a second aspect of the invention there is provided a method of manufacturing an electrical device comprising a manufacturing apparatus comprising an actuator for holding and moving an electronic component (e.g. so as to locate it with respect to another component of the electrical device), the manufacturing apparatus electrically connecting to the electronic component via at least one electrical connector when it is held (and for example) moved by the actuator. 
     Optionally, electrical power is supplied to the electronic component via the at least one electrical connector. Optionally, information is transferred between the electronic component and a processor device via the electrical connection. Such information can take the form of analogue or digital signals. Measurement data or other types of data (e.g. configuration and/or setup) can be transferred via the at least one electrical connector (e.g. to and/or from the electronic component). 
     The electrical device can comprise a readhead for an encoder apparatus. The electronic component can comprise a sensor configured to read a scale comprising a series of markings the output of which is configured for use in determining the relative position of the readhead and a scale. The method can comprise connecting to said sensor and reading signals from said sensor. 
     According to a further aspect of the invention there is provided, a readhead for an encoder apparatus, comprising a PCB comprising a sensor for detecting a scale, and at least one electrical connector provided on its surface extending between its faces which provide for electrical connection to the sensor. 
     This application also describes, a method of manufacture comprising a manufacturing apparatus comprising an actuator picking up a printed circuit board and in which an electrical connection to the printed circuit board is provided via at least one apparatus contact which is biased laterally onto a corresponding board contact on said printed circuit board. 
     The manufacturing apparatus can electrically connect to the printed circuit board via a plurality of apparatus contacts, each of which are biased laterally onto corresponding board contacts on said printed circuit board. 
    
    
     
       Embodiments of the invention will now be described, by way of example only, with reference to the following drawings in which: 
         FIG. 1  is a schematic drawing of an electrical device, in particular a readhead for a position measurement encoder, made according to the method of the invention; 
         FIGS. 2 a  and 2 b    are top and bottom exploded views of the readhead of  FIG. 1 ; 
         FIGS. 3 and 4  are schematic ray diagrams schematically illustrating the generation of a resultant field at the incremental photodetector via the use of diffracted light so as to facilitate incremental reading of the readhead position; 
         FIG. 5  is a schematic drawing of one type of incremental detector suitable for use in a readhead according to the invention; 
         FIGS. 6 a  to 6 d    illustrate an apparatus for gripping and locating a printed circuit board (PCB) of the readhead of  FIGS. 1 and 2  within a body of the readhead; 
         FIG. 7  provides an upper perspective view of the apparatus of  FIG. 6 ; 
         FIGS. 8 a  and 8 b    are top and bottom perspective views of the grippers and electrical contacts of the apparatus of  FIG. 6  as they engage the PCB; 
         FIGS. 9 a  and 9 b    are top and bottom views of the apparatus of  FIG. 6 ; 
         FIG. 10  illustrates a flow chart according to the invention; and 
         FIG. 11  schematically illustrates the difference in length of the electrical contacts and the grippers of the apparatus of  FIG. 6 . 
     
    
    
     Referring to  FIG. 1  there is shown a readhead  4  which is part of a position measurement encoder apparatus  2 . The position measurement apparatus also comprises a scale  6 . Although not shown, typically in practice the readhead  4  will fastened to one part of a machine and the scale  6  to another part of the machine which are movable relative to each other. The readhead  4  is used to measure the relative position of itself and the scale  6  and hence can be used to provide a measure of the relative position of the two movable parts of the machine. In particular, the readhead  4  is configured to read the scale  6  such that their relative position and/or motion can be determined. In this embodiment the position measurement encoder apparatus is an optical encoder, in that the readhead  4  utilises electromagnetic radiation (EMR) in the infra-red to ultraviolet range in order read the scale  6 . In particular, and as described in more detail below, the readhead  4  comprises a light source  40  which is used to illuminate the scale  6 , and incremental  36  and reference  38  photodetectors in order to detect the scale  6 . 
     Typically, the readhead  4  communicates with a processor such as a controller  8  via a wired (as shown) and/or wireless communication channel. The readhead  4  can report the signals from its detectors (described in more detail below) to the controller  8  which then processes them to determine position information and/or the readhead  4  can itself process the signals from its detectors and send position information to the controller  8 . 
     In the embodiment described, the encoder apparatus  2  is an incremental encoder apparatus and comprises an incremental scale track  10  and a separate reference mark track  12 . The incremental track  10  comprises a series of periodic scale marks  14  which control the light reflected toward the readhead  4  to effectively form a diffraction grating. The incremental track  10  could be what is commonly referred to as an amplitude scale or a phase scale. As will be understood, if it is an amplitude scale then the features are configured to control the amplitude of light transmitted toward the readhead&#39;s incremental detector (e.g. by selectively absorbing, scattering and/or reflecting the light). As will be understood, if it is a phase scale then the features are configured to control the phase of light transmitted toward the readhead&#39;s incremental detector (e.g. by retarding the phase of the light). In the present embodiment, the incremental track  10  is an amplitude scale, but in either case, as explained in more detail below, the light interacts with the periodic scale marks  14  to generate diffracted orders. These diffracted orders then interact with a diffraction grating  26  provided by the readhead  4  (explained in more detail below) which then form a resultant signal on the readhead&#39;s incremental detector  36  such that relative motion can be detected and measured. 
     The reference track  12  comprises a reference position defined by a reference mark  16  which in this case provides a contrast feature compared to the rest of the reference track  12 . As will be understood, many other types of reference mark are possible, including reference marks that are embedded within the incremental scale track. Reference positions can be useful to enable the readhead  4  to be able to determine exactly where it is relative to the scale  6 . Accordingly, the incremental position can be counted from the reference position. Furthermore, such reference positions can be what are also referred to as “limit positions” in that they can be used to define the limits or ends of the scale  6  between which the readhead  4  is permitted to travel. 
     Referring to  FIGS. 2 a  and 2 b   , the readhead  4  comprises a body  20 , a lid  22 , a printed circuit board (PCB) assembly  24  and a glass plate  26  on part of which a diffraction grating is formed. Once the readhead  4  has been assembled, the PCB assembly  24  sits within the body  20  and the lid  22  is secured to the body  20  (e.g. via gluing, welding, crimping, or additional mechanical means such as via screws) such that the PCB assembly  24  is contained within the body  20 . The PCB assembly  24  comprises a PCB  27 , and a cable connector  34 , an incremental photodetector  36 , a reference mark photodetector  38 , a light source  40  and associated processing electronics, mounted on the PCB  27 . Furthermore, as shown, the glass plate  26  comprising the diffraction grating is mounted to a window region  28  on the underside of the body, and a cable  32  for carrying signals and power to and from the readhead  4  is connected to the PCB assembly  24  via corresponding connectors  34 ,  39  on the PCB  27  and cable  32 . 
     With respect to the incremental track  10 , light from the source  40  leaves the readhead  4  via a portion of the glass plate  26  that does not contain the diffraction grating and falls on the periodic scale marks  14 , which define a diffraction pattern. The light therefore diffracts into multiple orders, which then fall on the part of the glass plate  26  containing the diffraction grating. In the present embodiment, the readhead&#39;s diffraction grating is a phase grating. The light is then further diffracted by the readhead&#39;s diffraction grating into orders which then interfere at the incremental photodetector  36  to form a resultant field, in this case an interference fringe. 
     The generation of the interference fringe is explained in more detail with reference to  FIGS. 3 and 4 . As will be understood,  FIG. 3  is a very simplified illustration of the real optical situation encountered in an encoder apparatus. In particular, the situation is shown for only one light ray from the source whereas in fact an area of the incremental track  10  is illuminated by the source. Accordingly, in reality the optical situation shown in  FIG. 3  is repeated many times over along the length of the scale (i.e. over the area that is illuminated by the source), hence producing a long interference pattern at the detector, which is schematically illustrated in  FIG. 4 . Also, for illustrative purposes only the +/−1 st  orders are shown (e.g. as will be understood the light will be diffracted into multiple orders, e.g. +/−3 rd , +/−5 th , etc diffraction orders). The light is diffracted by the series of periodic features  14  in the incremental track  10  of the scale  6 , and the diffraction orders propagate toward the diffraction grating on the glass plate  26  where the light is diffracted again before forming a resultant field  42  (in this case an interference fringe, but could for example be modulated spot(s)) at the incremental detector  36 . As shown in  FIG. 4 , the resultant field  42  is produced by the recombination of diffracted orders of light from the diffraction grating on the glass plate  26  and scale  6 . 
     The incremental photodetector  36  detects the resultant field  42  (e.g. the interference fringes) to produce a signal which is output by the readhead  4  to an external device such as controller  8  via cable  32 . In particular, relative movement of the readhead  4  and scale  6  causes a change in the resultant field (e.g. movement of the interference fringes relative to the detector  36  or a change in intensity of the modulated spot(s)) at the incremental detector  36 , the output of which can be processed to provide an incremental up/down count which enables an incremental measurement of displacement. 
     The incremental detector  36  can comprise a plurality of photodiodes, for example. In particular, as will be understood, in embodiments in which an interference fringe  42  is produced at the incremental detector  36 , the incremental detector  36  can be in the form of an electro-grating, which in other words is a photo-sensor array which can for example comprise two or more sets of interdigitated/interlaced photo-sensitive sensors, each set detecting a different phase of the interference fringe  42  at the detector  36 . An example is illustrated in  FIG. 5 , in which a part of an incremental detector  36  is shown, and in which the photodiodes of four sets of photodiodes A, B, C and D are interdigitated, and the outputs from each photodiode in a set are combined to provide a single output, A′, B′, C′ and D′. As illustrated, at any one instant in time, all the photodiodes in any one set detect the intensity of same phase of the interference fringe (if the fringe period and sensor period are the same). More details of a scale and readhead of this type are described in U.S. Pat. No. 5,861,953, the entire contents of which are incorporated into this specification by this reference. As will be understood, the electrograting/photo-sensor array can take other forms, such as comprising only three sets of photodiodes that are interdigitated, and different layouts can be used. 
     Accordingly, as can be seen from the above it can be important to ensure good alignment between the diffraction grating on the glass plate  26  and the incremental photodetector  36 . A method and apparatus for achieving good alignment between these components is described below in connection with  FIGS. 6 to 11 . 
     In summary, the method involves (and the apparatus facilitates) tweaking the position of at least one of the components to be aligned (in this case the PCB assembly  24  with the incremental photodetector  36  on it) whilst monitoring the signal output from the electrical device&#39;s sensor that will be used in operation (i.e. in this case monitoring the output from the incremental photodetector  36 ) so as to achieve a good signal. 
     Accordingly, referring to  FIGS. 6 to 11 , the apparatus comprises a manufacturing apparatus  100  (only part of which is shown for clarity purposes) comprising a manipulator  101  for picking up and moving the PCB assembly  24 . The manipulator comprises first  102 , second  104  and third  106  grippers configured such that the first gripper  102  can engage one edge of the PCB assembly  24  and such that the second  104  and third  106  grippers can engage the opposite side of the PCB assembly  24 . Together, the first  102 , second  104  and third  106  can grip the PCB assembly  24  so as to hold and move the PCB assembly  24 . The manipulator also comprises first  108 , second  110  and third  112  sprung electrical contacts, for engaging corresponding electrical contacts provided on the edge of the PCB assembly  24 . In addition to these sprung electrical contacts, electrical contacts are provided by the second  104  and third  106  grippers. 
     The manufacturing apparatus  100  comprises drives (not shown) for moving the manipulator  101  (and hence a PCB assembly  24  held by the manipulator&#39;s grippers  102 ,  104 ,  106 ) in three orthogonal linear dimensions, X, Y and Z. It also includes drives for twisting, the manipulator  101  i.e. rotating it around the Z-axis (optionally, the manufacturing apparatus could comprise drives for moving the manipulator in more than one rotational degree of freedom). In this embodiment, the manufacturing apparatus  100  can control a PCB assembly  27  held in the manipulator  101  so as to twist it (i.e. rotate it) about an axis parallel to the Z-axis. The manufacturing apparatus  100  also comprises drives (not shown) for moving the first  102 , second  104  and third  106  grippers and the first  108 , second  110  and third  112  sprung electrical contacts so as to selectively engage/release the PCB assembly  24 . Furthermore, as will be understood, the manufacturing apparatus  100  comprises position feedback devices (e.g. position measurement encoders) which can be used to determine the position (and orientation) of the manipulator  101  and hence the position (and orientation) of a PCB assembly  27  held by the manipulator  101 . 
     The manufacturing apparatus  100  also comprises a holder (not shown) for the body  20  into which the PCB assembly  24  is to be located, and a stage (not shown) for holding and moving a scale element  114  in the Y and Z dimensions relative to the manipulator  101  (and hence the body  20  and PCB assembly  24 ). Again, position reporting devices (e.g. position measurement encoders) are provided for reporting the position of the stage (and hence the scale element  114 ) in the Y and Z dimensions. 
     The manufacturing apparatus comprises a processor device (schematically illustrated by reference numeral  120 ) for transmitting and/or receiving signals to/from the manipulator&#39;s electrical contacts (i.e. the first  108 , second  110  and third  112  sprung electrical contacts and the electrical contacts provided by the second  104  and third  106  grippers). This can be via a wired or wireless link. The same processor device  120  or a different processor device can also be configured to control the manufacturing apparatus  100 , in particular the manipulator  101 . 
     Referring to  FIG. 10 , a flow chart illustrating a process  200  according to the invention is shown. The method begins at step  202  at which the processor  120  controls the manipulator  101  to pick up the PCB assembly  24 . As illustrated by  FIG. 6 a   , this involves positioning the manipulator  101  such that the first  102 , second  104  and third  106  grippers, and the first  108 , second  110  and third  112  sprung electrical contacts are positioned either side of the PCB assembly  24  (which sits in a storage port (not shown)) and then, as illustrated by  FIG. 6 b   , this involves advancing the first  102 , second  104  and third  106  grippers, and the first  108 , second  110  and third  112  sprung electrical contacts toward the PCB assembly  24  such that they engage the PCB  27 . The PCB  27  has electrical contact pads on its circumferential edge which are located so as to engage the second  104  and third  106  grippers and the first  108 , second  110  and third  112  sprung electrical contacts. Accordingly, the step  204  of connecting to the PCB assembly&#39;s incremental photodetector  36  is achieved at the same time. 
     In the described example electrical power is supplied to the PCB assembly  24  via the second  104  and third  106  grippers, and the first  108 , second  110  and third  112  sprung electrical contacts are signal lines. For example, but not necessarily, one of sprung electrical contacts (e.g. the first sprung electrical contact  108 ) can be used as a communications line (e.g. to communicate commands to and/or from the PCB assembly  24 , and/or to communicate data to/from any memory devices provided as part of the PCB assembly  24 ), and the other two sprung electrical contacts (e.g. the second  110  and third  112  sprung electrical contacts) can be used to transmit signals from the incremental photodetector  36  to the processor device  120 . As will be understood, there can be various other configurations of signal lines. For example, in an embodiment in which the readhead  4  and for example the PCB assembly  24  comprises its own power source (e.g. a battery) electrical contacts for power supply could well be unnecessary. Furthermore, any embodiments in which a communications line is not necessary. Further still, some sensors only provide one signal output, and hence only one signal line would be necessary. Also as will be understood to be within the scope of the invention is an embodiment in which the sensor communicates with a processor device wirelessly, and hence it is possible that no physical electrical contact is necessary. 
     Referring briefly to  FIG. 11 , as illustrated, the sprung electrical contacts ( 108 ,  110 ,  112 ) are longer in length than the grippers ( 102 ,  104 ,  106 ). Furthermore, before the PCB assembly  24  is picked up by the manipulator  101 , it sits in a storage port which comprises a trapezoidal seat  150 . Accordingly, when the manipulator  101  is brought down over the PCB assembly  24 , the sprung electrical contacts are pushed out and away from the PCB assembly by the sloping sides of the trapezoidal seat  150 . The manipulator  101  can then bring the opposing grippers together, whilst the trapezoidal seat  150  keeps the sprung electrical contacts away from the PCB  24 . As the manipulator  101  lifts the PCB assembly  24  out of its storage port away from the trapezoidal seat  150 , the sprung electrical contacts spring back toward their original position, thereby engaging the edges of the PCB assembly  24 . Such a configuration avoids the sprung electrical contacts crashing into the PCB assembly  24  on the way to pick the PCB assembly  24  up and also ensures that the grippers have a good hold of the PCB  27  before the sprung electrical contacts exert any force on the PCB  27  (which could otherwise affect the positioning of the PCB assembly  24  within the manipulator  101 ). As will be understood, there are other ways of ensuring that the sprung electrical contacts  108 ,  110 ,  112  do not crash into the PCB assembly  24  and do not contact the PCB  27  until the grippers  102 ,  104 ,  106  have a good hold of the PCB  27 . For example, the PCB storage port could comprise pockets into which the sprung electrical contacts  108 ,  110 ,  112  slide as the manipulator  101  brings the grippers and sprung electrical contacts down towards the PCB assembly  24 . The pockets can then hold the sprung electrical contacts  108 ,  110 ,  112  back from contacting the PCB  27  until the grippers  102 ,  104 ,  106  have a good hold of the PCB  27  and the manipulator  101  lifts the PCB assembly  24  out of the storage port. 
     As illustrated by  FIGS. 6 c  and 6 d   , at step  206 , the manipulator  101  moves the PCB assembly  24  so as to locate it within the readhead&#39;s body  20 . The body  20  is held by the measurement apparatus  100  by a holder (not shown) at a point within the manipulator&#39;s  101  movement volume. At this point, the body  20  does not have the lid  22 , but it does have the glass plate  26  comprising the diffraction grating mounted within its window region  28 . As explained above, and as illustrated in  FIGS. 6 c , 6 d    and  7 , a scale element  114  having periodic features which effectively define a diffraction grating (e.g. like that the readhead  4  will see in the incremental track  10  on a scale  6  when in use) is located under the window  28  and hence the glass plate  26  and is mounted on a stage (not shown) which can be driven so as to move the scale element  114  in the Y-dimension and also in the Z-dimension. 
     At step  208 , the position of the PCB assembly  24  is tweaked by the manipulator  101 . In summary, this involves powering the PCB assembly  24  via the electrical contacts provided by the second  104  and third  106  grippers such that the light source  40  is activated and illuminates the scale element  114 . A resultant field in this case in the form of an interference fringe is then produced on the incremental photodetector  36  in the manner described above in connection with  FIGS. 3 and 4 . The incremental photodetector  36  produces signals in response to detection of the interference fringe, which varies with movement of the scale element  114 . Such signals are passed to the processor  120  for analysis via the second  110  and third  112  sprung electrical contacts. In summary, a method according to the invention involves the process of the processor  120  receiving signals from the incremental photodetector  36 , and analysing the signals whilst the scale element  114  is moved in the Y-dimension. The position of the PCB assembly  24  is tweaked until a desired signal (for example, of desired amplitude) is obtained from the incremental photodetector. 
     In one particular embodiment the method involves using the output from the incremental photodetector  36  sensor only to aid the positioning/tweaking (e.g. fine tuning) of the PCB assembly  24  in the Z-dimension and also its yaw orientation (i.e. its angular orientation about an axis through the centre of the PCB  27  parallel to the Z-axis). In particular, the method can comprise positioning the PCB assembly  24  at an initial position and orientation within the readhead&#39;s body  20 . The Z position/height of the PCB assembly  24  in the initial position can be set to be at a height which is expected to be too high. It can be advantageous initially not to place the PCB assembly  24  at what might be expected to be the final desired height in case in fact this is too low and therefore the PCB  27  crashes into the base of the body  20  and/or the PCB  27  causes any pre-applied glue between the PCB  27  and the base of the body  20  (which is ultimately to be used to stick the PCB assembly  24  to the body  20 ) to be squeezed too thinly. 
     The method can then involve moving the scale element  114  in the Y-dimension and the processor  120  monitoring the signals from the incremental photodetector  36 . The Z position/height of the scale element  114  can then be adjusted, and then again moved in the Y-dimension whilst the processor  120  monitors the signals from the incremental photodetector  36 . This can be repeated for a number of different heights of the scale element  114 . The incremental photodetector&#39;s  36  outputs for the different heights can be analysed to determine how to adjust the height of the PCB assembly  24  relative to the body  20  (e.g. to determine by how much the PCB assembly  24  should be lowered into the body  20 ) to achieve a good signal at the preferred ride height of the readhead  20  at which it will be ultimately be used. The height of the PCB assembly  24  relative to the body  20  can then be changed by the manipulator  101 . 
     The yaw orientation of the PCB assembly  24  can then be tweaked by moving the scale element  114  along the Y dimension for different yaw orientations of the PCB assembly  24  within the body (which can be effected by the manipulator  101  controlling the yaw orientation) and monitoring the signal from the incremental photodetector  36 . The incremental photodetector&#39;s  36  outputs for the different yaw orientations can then be analysed to determine at which yaw orientation to set the PCB assembly  24  relative to the body  20 . 
     If desired, the height of the PCB assembly  24  can be checked again by monitoring the output of the incremental photodetector  36  for different Z positions of the scale element  114 . 
     In this embodiment, the X, Y lateral positions and the pitch and roll orientations (angular orientations about axis parallel to the X and Y axes) are not adjusted/tweaked by the method of the invention. Rather they are set by assuming that the manipulator has correctly positioned/orientated the PCB assembly  24  relative to the body  20  in those dimensions/orientations. In the present example, such an assumption can be relied on by that the PCB assembly&#39;s  24  general position/orientation in those dimensions/orientations can be determined from knowledge of the position of the manipulator  101  (using feedback from position feedback devices on the manipulator  101 /manufacturing apparatus  100 ) and the body  20  which is held by the measurement apparatus&#39;  100  holder (i.e. in a fixed position). As will be understood, there may be some uncertainty in the exact position at which the PCB assembly  24  is held by the manipulator&#39;s grippers  102 ,  104 ,  106 . If so, a camera could be used to image/view the PCB assembly  24  once it has been picked up by the manipulator  101  such that its X and Y position can be determined. Also, especially if the camera has a relatively narrow depth of field, the camera can provide an approximate Z position of the PCB assembly  24  with respect to the manipulator  101 . 
     Furthermore, in the present example, the accuracy of the type of readhead described is not as sensitive to the placement of the incremental photodetector  36  of the PCB assembly  24  in the X and Y dimensions (nor its pitch and roll orientations) as it is to its placement and orientation in the Z dimension and yaw orientation, and hence tweaking/fine tuning of the PCB in the X and Y positions and the pitch and roll orientations is not as important as the tweaking/fine tuning of the PCB in the Z and yaw degrees of freedom. 
     As described above, the signal from the incremental photodetector  36  is monitored/analysed. As will be understood, the signal can be analysed as it is output from the incremental photodetector  36 . Optionally, the signal can be recorded in memory and analysed at a subsequent point, e.g. after all relevant signals at relative different heights/orientations have been obtained. 
     As will also be understood, exactly what aspect of the signal(s) that is analysed can depend on the particular various factors including the type of electronic device being manufactured, the type of signal(s) output by the electronic device&#39;s sensor and/or exactly how precisely located the sensor or other component needs to be positioned. For example, the method can involve looking at the amplitude of the signal(s). 
     In the present example, the incremental photodetector  36  outputs two (ideally) generally sinusoidal waves 90° out of phase from each other, commonly referred to as quadrature signals. Such signals can be used to produce a lissajous and one implementation of the signals can be used to determine the radius of the lissajous produced by the incremental photodetector&#39;s quadrature signals, and tweak the position and/or orientation in at least one degree of freedom until a radius within a desired tolerance band is achieved. 
     Once the processor  120  determines that the PCB assembly  24  is in a position at which the signal meets the predetermined criteria, the PCB assembly  24  is fixed in place. This could be achieved for instance via gluing the PCB  27  into place which, for example, can previously have been applied between the PCB  27  and the base of the body  20 , and for instance curing UV curable glue by directing UV light at glue between the base of the body  20  and the PCB  27 . In order to aid such curing via UV light, holes/windows/UV transmission regions or the like could be provided in the PCB, especially at the regions at which the glue is located, such that UV light can be shone through the PCB so as to cure the glue. 
     Once the PCB assembly  24  has been secured to the body  20 , the processor device  120  controls the manipulator  101  to cause it to retract the grippers  102 ,  104 ,  106  and sprung electrical contacts  108 ,  110 ,  112  so as to release the PCB assembly  24  from the manipulator  101 . The cable  32  can then be connected to the PCB connector  34  and the lid  22  applied to the body  20  (which can be done by the same manufacturing apparatus  100 , a different manufacturing apparatus or by a human for example). 
     In the described embodiment, the grippers and the sprung electrical contacts are biased against the PCB  27  in the same dimension. This ensures that the grippers and sprung electrical contacts do not fight each other which can lead to adverse movement of the PCB  27 . Furthermore, the electrical contacts and grippers are biased laterally across the PCB  27 , and in particular against an edge extending between the PCB&#39;s  27  planar faces. This avoids having to use up valuable space on the planar faces of the PCB  27 , and therefore helps keep the size of the PCB  27  to a minimum. However, as will be understood, this need not necessarily be the case. For instance, the manipulator could have electrical contact pins which engage a contact provided on at least one of the planar faces of the PCB  27 . Optionally, the grippers could engage the planar faces of the PCB  27 . 
     In the described embodiment, the signal from the incremental photodetector  36  is transferred to the processor device  120  via the electrical contacts provided via the first  108 , second  110 , third  112  sprung electrical contacts. As will be understood, this need not necessarily be the case. For instance, the PCB assembly  24  could comprise a wireless transmitter for sending the signals to the processor device  120  wirelessly. In this case, power could be supplied to the PCB assembly  24  via electrical contacts provided by the manipulator  101  which engage the PCB. Optionally, the PCB assembly  24  could comprise a battery for powering the PCB assembly  24 , including the light source, sensors and any wireless transmitter. 
     Optionally, data can be transferred between a memory device on the PCB  27  and the processor device  120  (or indeed another processor device). For instance, data (e.g. data for use during the manufacture or use of the readhead) could be loaded into (or indeed extracted from) a memory device on the PCB  27 . Examples of types of such data include product serial number, part number, calibration data, built date. 
     In the embodiment described above, the position of the PCB assembly  24  is manipulated by the manipulator  101 . However, as will be understood, just the position of the incremental photodetector  36  could be adjusted and then when the desired position has been found it can be fixed to the PCB  27 , which could have previously been mounted to the body. Optionally, the position of the glass plate  26  comprising the index grating could be manipulated instead of or as well as the PCB assembly  24 . In all cases, the signal from the incremental photodetector  36  can be used to determine the preferred relative position of the incremental photodetector  36  and the glass plate  26 . 
     In the embodiment described above the position encoder is an incremental encoder. Nevertheless, as will be understood, the invention is also applicable to other types of position encoder, including absolute encoders. For example, many absolute encoders, including those described in WO2010/049682 use a lens to detect an image of the scale. The invention can for example, be useful to aid alignment between the imaging lens and image sensor. 
     In the embodiments above, the electrical device is a readhead for an optical position measurement encoder apparatus. As will be understood, the invention can also be used to aid the manufacture of other electrical devices such as other types of position measurement encoders, including magnetic and capacitive position measurement encoders. Other examples include other types of sensors, such as temperature sensors, pressure sensors, probes, for example measurement probes, in particular position measurement probes such as the type used on coordinate positioning apparatus such as coordinate measuring machines (CMMs) and machine tools. 
     Our inventors have also found it to be useful to provide an electrical connection to an electronic component, such as a PCB, whilst its position is being manipulated during manufacture (even if not connecting to a sensor like in the above embodiments). For example, it can be useful to test PCB  27 /PCB assembly  24  function before assembly into the final product. It can also be useful to program the electronic component or extract build/test/other data from the electronic component. In particular, when connecting to a PCB, connecting via contacts provided on the edge of the PCB can be advantageous because it can save PCB space, reduce cost and also help avoid deformation of the PCB.