Patent Publication Number: US-2020277941-A1

Title: Shape memory alloy actuator bearings

Description:
The present application generally relates to techniques for manufacturing shape memory alloy (SMA) actuators, and in particular to techniques for providing bearings in SMA actuators. 
     In a first approach of the present techniques, there is provided a shape memory alloy (SMA) actuation apparatus comprising: a support structure; a moveable component supported on the support structure in a manner allowing movement of the moveable component relative to the support structure in two orthogonal directions perpendicular to a notional primary axis extending through the moveable component, the moveable component comprising a spring plate; and at least two shape memory alloy (SMA) actuator wires connected between the moveable component and the support structure and arranged to, on contraction, move the moveable component; wherein the support structure comprises a bearing sub-assembly comprising: a sacrificial body portion, and a plurality of metallic bearings arranged to allow movement of the plate of the moveable component relative to the support structure, the metallic bearings held apart by the sacrificial body portion, the sacrificial body portion being removable from the plurality of metallic bearings during manufacture/assembly of the SMA actuation apparatus. 
     In a second approach of the present techniques, there is provided a method for manufacturing a shape memory alloy (SMA) actuation apparatus comprising: providing a support structure, a moveable component supported on the support structure in a manner allowing movement of the moveable component relative to the support structure in two orthogonal directions perpendicular to a notional primary axis extending through the moveable component, the moveable component comprising a spring plate, and at least two shape memory alloy (SMA) actuator wires connected between the moveable component and the support structure and arranged to, on contraction, move the moveable component; providing a bearing sub-assembly on the support structure, the bearing sub-assembly comprising a sacrificial body portion, and a plurality of metallic bearings arranged to allow movement of the plate of the moveable component relative to the support structure, the metallic bearings held apart by the sacrificial body portion; attaching the plurality of metallic bearings on the support structure; and removing the sacrificial body portion from the plurality of metallic bearings, leaving the metallic bearings attached to the support structure. 
     In a third approach of the present techniques, there is provided a shape memory alloy (SMA) actuation apparatus comprising: a support structure; a moveable component supported on the support structure in a manner allowing movement of the moveable component relative to the support structure in two orthogonal directions perpendicular to a notional primary axis extending through the moveable component, the moveable component comprising a spring plate; and at least two shape memory alloy (SMA) actuator wires connected between the moveable component and the support structure and arranged to, on contraction, move the moveable component; wherein the support structure comprises: a support component comprising a plurality of integrated bearings arranged to allow movement of the moveable component relative to the support structure. 
     In a fourth approach of the present techniques, there is provided a method for manufacturing a shape memory alloy (SMA) actuation apparatus comprising: providing a first sheet of material comprising a plurality of support components, each support component comprising a plurality of integrated bearings; providing a second sheet of material comprising a plurality of conductive components; aligning the second sheet of material over the first sheet of material such that each of the conductive components is provided on top of a support component; and attaching the first sheet of material to the second sheet of material to form a plurality of support structures each comprising a conductive component attached to a support component; detaching, from the attached first and second sheets of material, a support structure; providing a moveable component supported on the support structure in a manner allowing movement of the moveable component relative to the support structure in two orthogonal directions perpendicular to a notional primary axis extending through the moveable component, the moveable component comprising a spring plate arranged to contact the integrated bearings of the support structure; and providing at least two shape memory alloy (SMA) actuator wires connected between the moveable component and the support structure and arranged to, on contraction, move the moveable component. 
     In a fifth approach of the present techniques, there is provided an apparatus comprising an SMA actuation apparatus of the types described herein. 
     The apparatus may be any one of: a smartphone, a camera, a foldable smartphone, a foldable image capture device, a foldable smartphone camera, a foldable consumer electronics device, an image capture device, a 3D sensing device or system, a consumer electronics device, a mobile computing device, a mobile electronic device, a laptop, a tablet computing device, an e-reader (also known as an e-book reader or e-book device), a computing accessory or computing peripheral device (e.g. mouse, keyboard, headphones, earphones, earbuds, etc.), a security system, a medical device (e.g. an endoscope), a gaming system, a gaming accessory (e.g. controller, headset, a wearable controller, etc.), an augmented reality system, an augmented reality device, a virtual reality system, a virtual reality device, a wearable device, a drone (aerial, water, underwater, etc.), an autonomous vehicle, and a vehicle (e.g. an aircraft, a spacecraft, a submersible vessel, a car, etc.). It will be understood that this is a non-exhaustive list of example apparatus. 
     The SMA actuation apparatus described herein may be used in devices/systems suitable for, for example, image capture, 3D sensing, depth mapping, aerial surveying, terrestrial surveying, surveying in or from space, hydrographic surveying, underwater surveying, scene detection, collision warning, security, medical imaging, facial recognition, augmented and/or virtual reality, advanced driver-assistance systems in vehicles, autonomous vehicles, gaming, gesture control/recognition, and robotic devices. 
     Preferred features are set out in the appended dependent claims. 
    
    
     
       Implementations of the present techniques will now be described, by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1A  shows a schematic cross-sectional view of a camera apparatus; 
         FIG. 1B  shows a plan view of an arrangement of SMA actuator wires along the optical axis of the camera apparatus of  FIG. 1A ; 
         FIG. 1C  shows a perspective view of an arrangement of SMA actuator wires in the camera apparatus of  FIG. 1A ; 
         FIG. 2A  shows a plan view of a bearing sub-assembly comprising a plurality of bearings, where the bearing sub-assembly is provided on a support component; 
         FIG. 2B  shows a perspective view of bearings attached to the support component and detached from a body portion of the bearing sub-assembly; 
         FIGS. 3A and 3B  show a schematic of how the arrangement of  FIG. 2B  may be manufactured from sheets of material; 
         FIG. 4  shows layers of an actuator comprising a support component with separate bearings; 
         FIG. 5  shows a flowchart of example steps to assemble a support structure of an SMA actuator; 
         FIG. 6  shows layers of an actuator comprising a support component with integrated bearings; 
         FIGS. 7A to 7F  show various forms of integrated bearings; and 
         FIG. 8  shows a flowchart of example steps to assemble a support structure of an SMA actuator. 
     
    
    
     Broadly speaking, embodiments of the present techniques provide methods for assembling and manufacturing shape memory alloy (SMA) actuator assemblies, which may also advantageously simplify the process of, speed-up the process of and/or reduce the cost of manufacturing SMA actuator assemblies. 
     A shape memory alloy (SMA) actuator assembly for actuating movement of a movable element in two dimensions perpendicular to a primary axis is described in International Patent Publications WO2013/175197 and WO2014/083318. Such actuators may be used for Optical Image Stabilization (OIS) in miniature cameras. These actuators comprise four SMA wires connected between a movable element and a fixed support. Each wire is connected at one of its ends to the movable element at a crimp (the moving crimp) and at its other end to the support structure (the static crimp). The actuator of WO2013/175197 is now described in more detail with reference to  FIGS. 1A to 1C . 
       FIG. 1A  shows a schematic cross-sectional view of a camera apparatus  1  that is an example of an SMA actuation apparatus, and is taken along the optical axis O (which is a notional, primary axis). In order to clearly describe the main parts of the camera apparatus  1 , the SMA actuator wires are not shown in  FIG. 1A , but subsequently described with reference to  FIGS. 1B and 1C . The camera apparatus  1  may be incorporated into any number of devices, such as a smartphone, a foldable smartphone, a foldable image capture device, a foldable smartphone camera, a foldable consumer electronics device, an image capture device, a 3D sensing device or system, a consumer electronics device, a mobile computing device, a mobile electronic device, a laptop, a tablet computing device, an e-reader (also known as an e-book reader or e-book device), a computing accessory or computing peripheral device, a security system, a medical device (e.g. an endoscope), a gaming system, a gaming accessory, an augmented reality system, an augmented reality device, a virtual reality system, a virtual reality device, a wearable device, a drone (aerial, water, underwater, etc.), an autonomous vehicle, and a vehicle (e.g. an aircraft, a spacecraft, a submersible vessel, a car, etc.). It will be understood that this is a non-exhaustive list of example apparatus. In some cases, miniaturization is an important design criterion of the camera apparatus  1 . 
     The camera apparatus  1  comprises a lens element  2  supported on a support structure  4  by a suspension system  7 , in a manner allowing movement of the lens element  2  relative to the support structure  4  in two orthogonal directions each perpendicular to the optical axis O. Thus, the lens element  2  is a moveable element/component. 
     The support structure  4  is a camera support supporting an image sensor  6  on the front side of the base  5  thereof. On the rear side of the base  5  there is mounted an IC (integrated circuit) chip  30  in which the control circuit  40  is implemented, and also a gyroscope sensor  47 . 
     The lens element  2  comprises a lens carrier  21  in the form of a cylindrical body supporting a lens  22  arranged along the optical axis O, although in general any number of lenses  22  may be provided. The camera apparatus  1  is a miniature camera in which the lens  22  (or lenses  22  if plural lenses are provided) has a diameter of less than or equal to 10 mm, more preferably less than or equal to 20 mm. 
     The lens element  2  is arranged to focus an image onto the image sensor  6 . The image sensor  6  captures the image and may be of any suitable type, for example a CCD (charge-coupled device) or a CMOS (complimentary metal-oxide-semiconductor) device. 
     The lens(es)  22  may be fixed relative to the lens carrier  21 , or alternatively may be supported on the lens carrier in a manner in which the lens  22  (or at least one lens  22  if plural lenses are provided) is moveable along the optical axis O, for example to provide focusing. Where the lens  22  is moveable along the optical axis O, a suitable actuation system (not shown) may be provided, for example using a voice coil motor or SMA actuator wires, such as that described in International Patent Publication No. WO2007/113478. 
     In operation, the lens element  2  is moved orthogonally to the optical axis O in two orthogonal directions, shown as X and Y relative to the image sensor  6 , with the effect that the image on the image sensor  6  is moved. This is used to provide optical image stabilization (OIS), compensating for image movement of the camera apparatus  1 , caused by, for example, hand shake. 
     In many known arrangements using SMA actuator wire to provide an OIS function, for example as disclosed in International Patent Publications WO2010/029316 and WO2010/089529, the OIS is provided by tilting the entire camera unit including the lens element and the image sensor, substantially as a rigid body. This method of compensating for user handshake does in principle give the best OIS performance, because aligning the lens element to the image sensor is difficult in miniature cameras and the manufacturing tolerances are very tight. In addition, the user handshake being compensated for is essentially a tilt to the camera, and so it makes intuitive sense that the compensation should also tilt the camera. However, in this example, OIS is performed differently in order to mitigate several other problems. 
     The first problem is that with the ‘camera tilt’ method, the image sensor is moving, relative to the fixed camera structure. This presents extreme difficulties in routing electrical connections from the image sensor to the fixed structure of the camera, and onto the mobile phone motherboard. Solutions to this centre around flexible printed circuits (FPCs) to route connections, but the FPC design remains challenging, owing to the large number of connections, and the high data rates. Therefore, it is highly desirable for the image sensor to remain stationary and fixed. 
     The second problem is that the camera tilt method implies that there is a camera structure comprising as a minimum the lens and image sensor, with support structures that must tilt inside a surrounding support structure. Because the camera has a finite footprint, the tilt of the camera means that the camera thickness (height) of the OIS camera must be greater than for an equivalent camera without OIS. In mobile phones, it is highly desirable to minimize the camera height. 
     The third problem is that by tilting the whole camera, it is difficult to package the tilting actuators without increasing the footprint of the camera over that of the camera without OIS. 
     Accordingly, in  FIG. 1A  the lens element  2  is moved linearly in two orthogonal directions, both perpendicular to the optical axis O which may be termed “shift” or “OIS-shift”. The resulting image compensation does not entirely reverse the effects of user handshake, but the performance is deemed sufficiently good, given the constraints described above, and in particular allows the size of the camera apparatus  1  to be reduced as compared to an apparatus using tilt. 
       FIG. 1B  shows a plan view of an arrangement of SMA actuator wires along the optical axis of the camera apparatus of  FIG. 1A . Each of the SMA actuator wires  11  to  14  is arranged along one side of the lens element  2 . Thus, the SMA actuator wires  11  to  14  are arranged in a loop at different angular positions around the optical axis O. Thus, the four SMA actuator wires  11  to  14  consist of a first pair of SMA actuator wires  11  and  13  arranged on opposite sides of the optical axis O and a second pair of SMA actuator wires  12  and  14  arranged on opposite sides of the optical axis O. The first pair of SMA actuator wires  11  and  13  are capable on selective driving to move the lens element  2  relative to the support structure  4  in a first direction in said plane, and the second pair of SMA actuator wires  12  and  14  are capable on selective driving to move the lens element  2  relative to the support structure  4  in a second direction in said plane transverse to the first direction. Movement in directions other than parallel to the SMA actuator wires  11  to  14  may be driven by a combination of actuation of these pairs of the SMA actuator wires  11  to  14  to provide a linear combination of movement in the transverse directions. Another way to view this movement is that simultaneous contraction of any pair of the SMA actuator wires  11  to  14  that are adjacent each other in the loop will drive movement of the lens element  2  in a direction bisecting those two of the SMA actuator wires  11  to  14  (diagonally in  FIG. 1B , as labelled by the arrows X and Y). 
     As a result, the SMA actuator wires  11  to  14  are capable of being selectively driven to move the lens element  2  relative to the support structure  4  to any position in a range of movement in two orthogonal directions perpendicular to the optical axis O. The magnitude of the range of movement depends on the geometry and the range of contraction of the SMA actuator wires  11  to  14  within their normal operating parameters. 
       FIG. 1C  shows a perspective view of an arrangement of SMA actuator wires in the camera apparatus of  FIG. 1A . The actuator arrangement  10  comprises a total of four SMA actuator wires  11  to  14  connected between a support block  16  that forms part of the support structure  4  and is mounted to the base  5  and a movable platform  15  that forms part of the lens element  2  and is mounted to the rear of the lens plate  73  as shown in  FIG. 1A . 
     Each of the SMA actuator wires  11  to  14  is held in tension, thereby applying a force between the movable platform  15  and the support block  16  in a direction perpendicular to the optical axis O. In operation, the SMA actuator wires  11  to  14  move the lens element  2  relative to the support block  16  in two orthogonal directions perpendicular to the optical axis O. 
     The SMA actuator wires  11  to  14  are connected at one end to the movable platform  15  by respective crimping members  17  and at the other end to the support block  16  by crimping members  18 . The crimping members  17  and  18  crimp the wire to hold it mechanically, optionally strengthened by the use of adhesive. The crimping members  17  and  18  also provide an electrical connection to the SMA actuator wires  11  to  14 . However, any other suitable means for connecting the SMA actuator wires  11  to  14  may alternatively be used. 
     The present techniques provide improvements to the design and assembly of such an actuator and camera module. 
     To enable the moveable component of the above-described actuator to move relative to the support structure, bearings are provided between the support structure and moveable component. Ball bearings may be used to enable the movement of the moveable component. Alternatively, plain bearings may be provided on the support structure to enable the movement of the moveable component. However, the plain bearings are typically provided as individual pieces of material that are attached to the support structure. A problem that arises when using plain bearings (also referred to as bearing surfaces) is that the individual pieces of material may be difficult to accurately place/position on the support structure. Furthermore, bearing surfaces need insulating from other conductive elements. A solution to these problems may be to form the bearing surfaces from an etched component having partially etched regions that define bearings, and using the etched component to position and attach the bearings onto the support structure. The bearings may then be cut from the etched component. Specifically, the bearings may be attached to a support component, which may be a laminate of an insulator on top of a thin structural layer. As the support component comprises an insulator, the bearings may be insulated from other conductive elements when attached to the support component. 
       FIG. 2A  shows a plan view of an intermediate assembly  200  used to assemble a support structure of an SMA actuator. The intermediate assembly  200  comprises a bearing sub-assembly  206  comprising a plurality of bearings  210 , where the bearing sub-assembly  206  is provided on a support component  202 . The intermediate assembly  200  may comprise the support component  202 , a conductive component  204 , and a bearing sub-assembly  206 . The bearing sub-assembly  206  may comprise a sacrificial body portion, and a plurality of metallic bearings  210  held apart by the sacrificial body portion, where the sacrificial body portion is removable from the plurality of metallic bearings  210 . The bearing sub-assembly  206  may be formed by etching a sheet of metallic material. The metallic bearings  210  are held apart from each other, and in the required position for attaching to the support component  202 , by arms  214  of the sacrificial body portion. Each arm  214  comprises a partially-etched region  208  and a bearing  210 . The partially-etched region  208  is thinner than the bearing  210 . The bearing  210  has a thickness or height that means it protrudes from the support structure  200 . The sacrificial body portion may comprise flexure arms  212  (only part of the flexure arms are shown here—the flexure arms  212  are also shown in  FIGS. 3A and 3B ). The flexure arms  212  may be used to hold and guide the bearing sub-assembly  206  into the required position on the support component  202 . The flexure arms  212  allow the position of the bearing sub-assembly  206  above the support component  202  to be changed, while constraining lateral movement of the bearing sub-assembly  206  (i.e. movement in a  2 D plane above the support component). The flexure arms  212  are flexible, such that the bearing sub-assembly  206  may be pushed down onto the support component  202  to achieve good contact between the base/bottom of the bearings  210  and partially-etched regions  208  and the support component  202  during the attachment process. The whole of the bearing sub-assembly  206  may be flexible. 
     The bearing sub-assembly  206  may be provided in a sheet of material (i.e. may be etched into the sheet of material). The bearing sub-assembly  206  may be attached to the sheet of material by the flexure arms  212 . The bearing sub-assembly may be pushed onto the support component  202  from the sheet of material (which is enabled by the flexible flexure arms  212 ). 
       FIG. 2B  shows a perspective view of the bearings  210  and partially-etched regions  208  attached to the support component  202 , and detached from the body portion of the bearing sub-assembly  206 . The partially-etched regions  208  are detached from the body portion (i.e. the arms  214 ) by mechanically cutting or laser cutting along lines  218 . The partially-etched regions  208  have a lower height than the bearings  210  so that when the partially-etched regions  208  are cut from the arms  214  along lines  218 , any burr that forms during the cutting process also has a lower height than the bearings  210 . 
     Thus, embodiments of the present techniques provide a shape memory alloy (SMA) actuation apparatus comprising: a support structure  200 ; a moveable component supported on the support structure in a manner allowing movement of the moveable component relative to the support structure in two orthogonal directions perpendicular to a notional primary axis extending through the moveable component, the moveable component comprising a spring plate; and at least two shape memory alloy (SMA) actuator wires connected between the moveable component and the support structure and arranged to, on contraction, move the moveable component; wherein the support structure comprises a bearing sub-assembly  206  comprising: a sacrificial body portion, and a plurality of metallic bearings  210  arranged to allow movement of the plate of the moveable component relative to the support structure, the metallic bearings  210  held apart by the sacrificial body portion, the sacrificial body portion being removable from the plurality of metallic bearings  210  during manufacture/assembly of the SMA actuation apparatus. 
     The support structure of the SMA actuation apparatus comprises a support component  202 , and the metallic bearings  210  are attached to the support component  202 . 
     The support structure of the SMA actuation apparatus may comprise a conductive component  204  which is supported on, and attached to, the support component  202 . The support component  202  must be electrically-isolated. Thus, the support component  202  may be formed of an insulator (e.g. a polymer) and the metallic bearings  210  may be attached to the support component  202  by an adhesive or electrically insulative adhesive. Alternatively, the support component  202  may be formed of a metal or metal alloy, and the conductive component  204  and the metallic bearings  210  may be attached to the support component  202  by an electrically insulative adhesive material. 
     Alternatively, the support component  202  may have a laminate structure, comprising an electrically insulative material provided on a metal structural layer, and the metallic bearings  210  may be attached to the support component  202  by adhering the metallic bearings  210  to the electrically insulative material. The metal structural layer may be formed of steel or stainless steel. The structural layer may have a thickness of less than or equal to 50 μm. The electrically insulative layer may be a polymer, such as parylene/a parylene polymer. The electrically insulative layer may have a thickness of less than or equal to 10 μm. In some cases, the electrically insulative material may be provided on both sides of the structural layer. 
     The metallic bearings  210  may be formed of any one of: a metal, a metal alloy, stainless steel, steel, bearing bronze, and phosphor bronze. It will be understood that these are just some example materials that may be used to form the metallic bearings  210 . 
     The metallic bearings  210  may be coated with a friction-reducing or low-friction coating. For example, the metallic bearings  210  may be coated with any one of: a lubricant, a dry film lubricant, a diamond-like carbon coating, and hard chrome. Alternatively, a surface of the metallic bearings  210  which contacts the spring plate of the moveable component may be polished (by a mechanical polishing process, electro-polishing process or chemical polishing process). The polishing process may be performed while the metallic bearings  210  are still attached to the sacrificial body portion of the bearing sub-assembly. 
     In addition to coating/polishing the metallic bearings  210 , or as an alternative to coating/polishing the metallic bearings  210 , at least a side of the spring plate (of the moveable component) that is in contact with the metallic bearings  210  may be coated with a friction-reducing or low-friction coating. The side of the spring plate in contact with the metallic bearings  210  may be coated with any one of: a lubricant, a dry film lubricant, a diamond-like carbon coating, hard chrome, and a hard chrome plating. Alternatively, at least a side of the spring plate in contact with the metallic bearings  210  may be polished for friction reduction (by a mechanical polishing process, electro-polishing process or chemical polishing process). 
     The support structure  200  further comprises a conductive component  204  comprising wire attach structures  220  (e.g. crimps) for coupling one end of each SMA actuator wire to the support structure. 
     The conductive component  204  is attached to the support component  202 . 
     The metallic bearings  210  may be attached to the support component  202  by: providing the bearing sub-assembly  206  on the support component  202 ; attaching the metallic bearings  210  to the support component  202 ; and detaching the metallic bearings  210  from the sacrificial body portion of the bearing sub-assembly  206  (along the detachment points/lines  218 ). The metallic bearings  210  may be detached from the sacrificial body portion of the bearing sub-assembly  206  by any one of: a mechanical cutting process, or laser cutting process. 
     In embodiments, the SMA actuation apparatus may be a camera apparatus further comprising an image sensor fixed to the support structure. The moveable component may comprise a camera lens element comprising at least one lens arranged to focus an image on the image sensor. In this case, the primary axis is the optical axis of the camera lens element. The moveable component may be moved to provide optical image stabilization. 
     In embodiments, the SMA actuation apparatus  400  may comprise a total of four SMA actuator wires. 
       FIGS. 3A and 3B  show a schematic  300  of how the support structure  200  of  FIG. 2B  may be manufactured from several sheets of material. A first sheet of material  306  comprises a plurality of support components, where each support component is used to form one SMA actuation apparatus. A second sheet of material  304  comprises a plurality of conductive components. Each conductive component comprises wire attach structures (e.g. crimps) for coupling one end of each SMA actuator wire to the support structure. A third sheet of material  302  comprises a plurality of bearing sub-assemblies  206 , each bearing sub-assembly  206  comprising a plurality of metallic bearings. Each bearing sub-assembly  206  is attached to the third sheet of material  302  by flexure arms  212 . The entire third sheet of material  302 , apart from the metallic bearings, may be considered the sacrificial body portion. 
     In  FIGS. 3A and 3B  the sheets of material  302 ,  304 ,  306  comprise five support component components, conductive components and bearing sub-assemblies, such that five support structures can be assembled for five SMA actuators. However, it will be understood that each sheet of material  302 ,  304 ,  306  may comprise any number of components. The sheets of material may be strips (as shown) comprising a row of components, or may comprise several rows (i.e. an array) of components. 
     The second sheet of material  304  is provided over the first sheet of material  306  such that each of the conductive components is provided on top of a support component. The first sheet of material  306  is attached to the second sheet of material  304 . The second sheet of material  304  may be aligned over the first sheet of material  306  by aligning guiding features  312 ,  314  on the first and second sheets of material. One or more of the guiding features  312 ,  314  may be holes and a pin may be inserted through the holes to assist the alignment. 
     The third sheet of material  302  is provided over the second sheet of material  304  and aligned to the, now attached, first and second sheets of material  304 ,  306 . The metallic bearings of each bearing sub-assembly  206  of the third sheet of material  302  are attached to the support component components. Several support structures are now assembled and may be detached from the sheets of material as and when required to assemble an SMA actuator. 
       FIG. 4  shows an exploded view of layers of an SMA actuator  400  comprising separate bearings  210 . The SMA actuator  400  comprises a support structure comprising a support component  202  and a conductive component  204 . Bearings  210  are attached to support component  202 . The support component  202  may be attached to a base layer  402 . The SMA actuator  400  comprises a spring plate  404  of a moveable component. The spring plate  404  is connected to wire attach structures/crimps  405 . The spring plate  404  is in contact with the bearings  210 , such that the spring plate  404  (and therefore the moveable component) is moveable relative to the support structure. The SMA actuator  400  comprises SMA actuator wires  406 , which are each attached at one end to wire attach structures/crimps  405  moveable component and at another end to wire attach structures/crimps of the conductive component  204 . 
       FIG. 5  shows a flowchart of example steps to assemble a support structure of an SMA actuator. The process begins by providing a first sheet of material comprising a plurality of support component components (step S 500 ), and providing a second sheet of material comprising a plurality of conductive components (step S 502 ). The process comprises aligning the second sheet of material over the first sheet of material such that each of the conductive components is provided on top of a support component (step S 504 ), and attaching the first sheet of material to the second sheet of material to form a plurality of support structures each comprising a conductive component attached to a support component (step S 506 ). 
     The step S 504  of aligning the second sheet of material over the first sheet of material may comprise aligning guiding features on the first and second sheets of material. 
     Once the first and second sheets of material have been attached, the process comprises providing a third sheet of material comprising a plurality of bearing sub-assemblies (step S 508 ), and aligning the third sheet of material on the attached first and second sheets of material where each bearing sub-assembly is provided on top of a support structure (step S 510 ). 
     The process comprises attaching the plurality of metallic bearings of each bearing sub-assembly on the corresponding support structure (step S 512 ). The attachment process may comprise adhering the metallic bearings to the support component. 
     The process comprises detaching the metallic bearings from the sacrificial body portion of each bearing sub-assembly (step S 514 ), and then detaching the assembled support structures from the sheets of material (step S 516 ). 
     An alternative solution to the above-described problems is to provide a support component with integrated bearings. This solution avoids the need to position the bearings on the support component, and for separate pieces of material to be used to form the bearings. Thus, the solution may provide a cheaper and easier to assemble SMA actuator. 
       FIG. 6  shows an exploded view of layers of an SMA actuator  600  comprising integrated bearings  606 . The SMA actuator  600  comprises a support structure comprising a support component  604  and a conductive component  204 . Integrated bearings  606  are formed in the support component  604 . The integrated bearings  606  may be formed by partially-etching the support component  604  (e.g. using a laser etching or chemical etching process). Thus, much of the material of the support component  604  is removed by the partial-etching process to form the integrated bearings  606 . The support component  604  may be attached to a base layer  602 . The SMA actuator  600  comprises a spring plate  608  of a moveable component. The spring plate  608  is attached to wire attach structures/crimps  609 . The spring plate  608  is in contact with the integrated bearings  606 , such that the spring plate  608  (and therefore the moveable component) is moveable relative to the support structure. The SMA actuator  600  comprises SMA actuator wires  610 , which are each attached at one end to wire attach structures/crimps of the moveable component and at another end to wire attach structures/crimps of the conductive component  204 . 
     Thus, embodiments of the present techniques provide a shape memory alloy (SMA) actuation apparatus comprising: a support structure; a moveable component supported on the support structure in a manner allowing movement of the moveable component relative to the support structure in two orthogonal directions perpendicular to a notional primary axis extending through the moveable component, the moveable component comprising a spring plate  608 ; and at least two shape memory alloy (SMA) actuator wires  610  connected between the moveable component and the support structure and arranged to, on contraction, move the moveable component; wherein the support structure comprises: a support component  604  comprising a plurality of integrated bearings  606  arranged to allow movement of the moveable component relative to the support structure. 
     The integrated bearings  606  may be raised portions formed in a surface of the support component  604 . 
     The support structure of the SMA actuation apparatus may comprise a conductive component  204  which is supported on, and attached to, the support component  604 . The support component  604  must be electrically-isolated. Thus, the support component  604  may have a laminate structure comprising an electrically insulative material provided on a metallic structural layer. The structural layer may be formed of steel or stainless steel. The structural layer may have a thickness of less than or equal to 50 μm. The electrically insulative layer may have a thickness of less than or equal to 10 μm. In some cases, the electrically insulative material may be provided on both sides of the structural layer. The electrically insulative material may be a hard-wearing, low friction and insulative material (but not a polymer). Example suitable materials include a diamond-like carbon coating (DLC), tungsten-DLC and a tungsten carbon carbide coating (WC/C). In embodiments, a single material may be both low friction and insulating. In embodiments, the metal structural layer may be coated with a first material which is electrically insulative, and a second material which is low friction. 
     At least the integrated bearings  606  of the support component  604  may be coated with a friction-reducing or low-friction coating. The integrated bearings  606  may be coated with any one of: a lubricant, a dry film lubricant, a diamond-like carbon coating, hard chrome, and a hard chrome plating. Additionally or alternatively, at least a side of the spring plate  608  in contact with the integrated bearings  606  may be coated with a friction-reducing or low-friction coating. The side of the spring plate  608  in contact with the integrated bearings  606  may be coated with any one of: a lubricant, a dry film lubricant, a diamond-like carbon coating, hard chrome, and a hard chrome plating. Alternatively, at least a side of the spring plate  608  in contact with the integrated bearings  606  may be polished for friction reduction. 
       FIGS. 7A to 7F  show various forms of integrated bearings  606 . It will be understood that these are just some examples of the form/shape of the integrated bearings  606  and are non-limiting.  FIG. 7A  shows a perspective view of an integrated bearing  606  that has a raised boss-like structure, and  FIG. 7B  shows how the raised boss  606  may be formed from the support component  604 . The raised bosses  606  could be created by using a metal forming process on a support component  604  which is formed of a thin sheet of metal. The raised bosses  606  may be formed by domed impressions or structures in the base layer  602 : when the support component  604  is attached to the base layer  602 , the domed structures of the base layer  602  may cause the raised bosses  606  to be formed. 
     In some cases, forming a raised boss may be difficult.  FIGS. 7C to 7E  show how an integrated bearing  606  may be formed by etching reliefs  700  into the material of the support component  604  such that the bearing  606  may be formed without tearing the material. 
       FIG. 7F  shows how an integrated bearing  606  may be formed by etching/cutting a tab into the support component  604 , and forming-up the tab (e.g. using a two bend-point forming operation) to provide a bearing  606 . This type of integrated bearing  606  may be weaker than the bearings shown in  FIGS. 7A to 7E . 
     Thus, in embodiments, the integrated bearings  606  may be formed by partially-etching the support component  604 . Alternatively, the integrated bearings  606  may be provided by forming raised portions in a surface of the support component  604 . Alternatively, the integrated bearings  606  may be provided by etching and forming raised portions in a surface of the support component  604 . Alternatively, the integrated bearings  606  may be provided by cutting tab portions in the support component  604  and forming-up the tab portions. 
     The support structure may further comprise a conductive component  204  comprising wire attach structures for coupling one end of each SMA actuator wire to the support structure. The conductive component  204  is attached to the support component  604 . 
     In embodiments, the SMA actuation apparatus may be a camera apparatus further comprising an image sensor fixed to the support structure. The moveable component may comprise a camera lens element comprising at least one lens arranged to focus an image on the image sensor. In this case, the primary axis is the optical axis of the camera lens element. The moveable component may be moved to provide optical image stabilization. 
     In embodiments, the SMA actuation apparatus  600  may comprise a total of four SMA actuator wires. 
       FIG. 8  shows a flowchart of example steps to assemble a support structure of an SMA actuator. The process comprises providing a first sheet of material comprising a plurality of support components, each support component comprising a plurality of integrated bearings (step S 800 ), and providing a second sheet of material comprising a plurality of conductive components (step S 802 ). The process comprises aligning the second sheet of material over the first sheet of material such that each of the conductive components is provided on top of a support component (step S 804 ). The first sheet of material is attached to the second sheet of material to form a plurality of support structures each comprising a conductive component attached to a support component (step S 806 ). The process then comprises detaching, from the attached first and second sheets of material, a support structure (step S 808 ). 
     A moveable component is then provided on the assembled support structure and supported on the support structure in a manner allowing movement of the moveable component relative to the support structure in two orthogonal directions perpendicular to a notional primary axis extending through the moveable component, the moveable component comprising a spring plate arranged to contact the integrated bearings of the support structure. 
     At least two shape memory alloy (SMA) actuator wires are then connected between the moveable component and the support structure and arranged to, on contraction, move the moveable component. 
     Embodiments of the present techniques provide an SMA four-wire actuator assembly comprising three or more bearings to allow movement of the moveable element on a support structure wherein the bearings are assembled into the actuator from an etched component which is subsequently de-tabbed. 
     Those skilled in the art will appreciate that while the foregoing has described what is considered to be the best mode and where appropriate other modes of performing present techniques, the present techniques should not be limited to the specific configurations and methods disclosed in this description of the preferred embodiment. Those skilled in the art will recognize that present techniques have a broad range of applications, and that the embodiments may take a wide range of modifications without departing from any inventive concept as defined in the appended claims.