Abstract:
A method and system include a cable including a plurality of conductors terminating at a leading edge of the cable, and markers disposed at the leading edge providing visual reference points at one or more predetermined positions, the markers being separate from the plurality of conductors.

Description:
TECHNICAL FIELD 
   The invention relates in general to manufacturing electronic components and specifically relates to the manufacture of transducer arrays for a variety of systems. 
   BACKGROUND OF THE INVENTION 
     FIG. 1  is an illustration of example ultrasound transducer  100 . Transducer  100  includes, among other things, cable  101  that carries signals between transducer  100  and a processing and control unit (not shown). Transducer  100  also includes body  102  for providing a handle shape for an ultrasound operator to grip transducer  100  when performing an ultrasound examination. Surface  103  of transducer  100  contacts a patient or other subject and includes a plurality of individual transducer elements that transmit and receive acoustic waves during an examination. The processing and control unit controls the beam forming in transducer  100  and also processes the electrical signals produced by the transducer elements as the elements receive reflected acoustic waves during an examination. 
     FIG. 2  is an exploded view of example components  200  inside transducer  100 . As shown, cable  101  is connected to flex circuit  202 , and flex circuit  202  is connected to transducer array  201  such that the control and processing unit (not shown) is in electrical communication with transducer array  201 . Transducer array  201  includes individual acoustic transducer elements  204 , which, in this example, are individually controlled active acoustic elements that produce acoustic waves from electrical stimulation and produce electrical signals in response to receiving reflected acoustic waves. Transducer array  201  is usually fabricated as an “acoustic stack”—one or more ceramic or polymer layers that are metallized on both sides. As explained more fully below, the acoustic stack is cut into a plurality of individual transducer elements. The ceramic or polymer itself is not electrically conductive, but is a piezoelectric material that may be excited by applying a high voltage across its two outer surfaces. The control and processing unit detects minute voltage fluctuations in the signal received from array  201  and performs digital signal processing to produce an image for a human user. 
   Flex circuit  202  is an intermediary device to connect relatively rigid cable assembly  101  to fragile, small, and minute acoustic elements  204 . Flex circuit  202 , in this example, is a flexible printed circuit that includes a plurality of signal traces  203  and is similar in some respects to a ribbon. In some examples, flex circuit  202  includes signal traces on a layer of KAPTON™, which is a non-conducting, flexible polymer available from E.I. du Pont de Nemours and Company, that provides flexible support to the traces. 
   The current art provides for several ways to create an electrical connection between the system electronic circuits in the control and processing unit and the plurality of acoustic elements. Specifically, the prior art provides methods of electrically attaching cable assemblies from the control and processing unit to the acoustic stack itself. One example process includes embedding flex circuit  202  in a block of backing material (not shown), which helps to support both the acoustic stack and the flex circuit  202  during manufacturing and use and also helps to dampen acoustic vibrations in the assembly. A leading edge of flex circuit  202  is visible and exposed at a surface of the backing material so that an electrical connection can be made between flex circuit  202  and the acoustic stack by placing the acoustic stack on the surface so that it contacts flex circuit  202 . No soldering is used. The dicing saw operator then cuts through the acoustic stack and the backing material between each of signal traces  203  to create electrically isolated acoustic elements  204 . An example method for attaching a backing block and conductive elements to an acoustic stack without soldering is described in U.S. Pat. No. 6,104,126, issued Aug. 15, 2000, the disclosure of which is hereby incorporated herein by reference. 
   In contrast, current industry standards include soldering flex circuit  202  to the exposed metallized face or edges of the acoustic stack before dicing. A difficulty with both methods is that the exposed leading edge of flex circuit  202  is underneath the acoustic stack, thereby obscuring the signal traces and making the dicing operation more challenging. 
     FIG. 3  is an illustration of example flex circuit assembly  300 . Flex circuit  202  ( FIG. 2 ) includes KAPTON™ layer  303  and a plurality of signal traces  203 . Assembly  300  includes backing block  301 , which is made of a more rigid, nonconductive material (e.g. acoustic backing material) that surrounds flex circuit  202 . Assembly  300  includes surface  304  where a leading edge of flex circuit  202  is visible. In order to guide the dicing saw operator, the assembly line (or the saw operator) scribes backing block  301  with marks  302  (i.e., kerfs) to the edges of block  301 . Marks  302  are produced by making shallow cuts in block  301  between the signal traces, thereby transferring a datum feature to the outside of block  301 . Marks  302  may then be seen by the saw operator after the acoustic stack is laid down on block  301 . Marks  302  indicate spaces between the signal traces where cuts should be made. Marks  302  may be made for each signal trace or may be spaced apart by multiple signal traces in a pattern. In the example of  FIG. 3 , marks  302  are spaced at every third signal trace. 
   In both examples above, the dicing cuts and the kerfs are based on the positions of the actual signal traces in the leading edge of flex circuit  202 . However, in some applications, discrete signal traces at the leading edges may not be available, making the above-described methods unusable. 
   BRIEF SUMMARY OF THE INVENTION 
   Various embodiments of the present invention are directed to systems and methods which include alignment markers in the flex circuit that are separate from the signal-carrying conductors. From the markers, scoring marks can be made on the backing block to guide a dicing saw. Alternatively, a dicing saw operator can guide the saw based on the markers, themselves. Example manufacturing techniques connect the signal traces in a buss at the leading edge of the flex circuit, thereby visually obscuring the individual signal traces at the leading edge. Accordingly, various embodiments of the invention may add utility to such techniques by providing alignment markers that are different and/or electrically isolated from the buss and the signal traces. 
   In one example embodiment, the flex circuit is made of a number of layers with the alignment markers on a layer different than the layer that includes the signal carrying traces. For instance, the markers may be included on a layer that is used for a ground plane and insulated from the signal carrying conductors by a flexible insulating layer. The markers indicate the positions of the signal traces and are exposed and/or visible at the leading edge of the flex cable. The alignment markers may be used to make kerfs or dices. In another example embodiment, the flex circuit includes a strip of material that protrudes out from the backing block and includes alignment markers. When the acoustic stack is placed on the backing block, the strip is folded down, and portions of the strip extend past the edge of the stack, thereby providing a visual indicator for the dicing saw operator to make cuts. 
   The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
       FIG. 1  is an illustration of an example ultrasound transducer; 
       FIG. 2  is an exploded view of example components inside an example transducer; 
       FIG. 3  is an illustration of an example flex circuit assembly; 
       FIG. 4  is an illustration of an example flex circuit assembly according to one embodiment of the invention; 
       FIG. 5  is an illustration of an example flex circuit assembly according to one embodiment of the invention; 
       FIG. 6  is a flowchart of an example method for manufacturing a transducer device with the flex circuit assembly of  FIG. 4 ; and 
       FIG. 7  is a flowchart of an example method for manufacturing a transducer device with the flex circuit assembly of  FIG. 5 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 4  is an illustration of example flex circuit assembly  400  according to one embodiment of the invention. Assembly  400  includes backing block  406 , and embedded signal traces  402  are present inside backing block  406  but cannot be seen by a human operator. Flex circuit  407  includes buss  404 , which terminates and shorts signal traces  402  at the leading edge thereof, so that a human operator sees a line of copper or other conducting material when viewing surface  405 . When the operator dices the acoustic stack (not shown), the cuts extend past the depth of buss  404 , thereby creating individual contacts out of a once continuous strip of conducting material. Buss  404 , once it is diced, provides wide contacts between the transducer elements and their respective signal traces  402 . An advantage of using buss  404  rather than individual signal traces at the leading edge of flex circuit  407  is that the buss provides wider contacts, and the reliability and signal conducting quality of a contact usually increases with its width. 
   The flex circuit also includes flexible insulating layer  408 , possibly made of KAPTON™, that provides some support to traces  402 . Despite its name, however, flex circuit  407  is not required to be flexible, as insulating layer  408  may be constructed of fiberglass or other more relatively rigid material. 
   When dicing or scribing marking lines on surface  405 , an operator cannot rely on visual inspection of traces  402  to determine their positions because signal traces  402  are not visible at the leading edge. Therefore, the prior art methods described above provide little utility in this example. Accordingly, flex circuit  407  includes markers  401  that indicate positions of signal traces  402 . Alignment markers  401  may be aligned with signal traces  402  or may be aligned with spaces between signal traces  402 , in which case, markers  401  would implicitly (rather than explicitly) indicate the positions of traces  402 . The invention is not limited to any particular method of alignment as long as a person or machine may determine or infer placement of traces  402  from markers  401 . 
   Markers  401  may be produced, for example, by laying down an additional layer of conducting material on flex circuit  407 . Typical flex circuits include several alternating layers of insulating material (e.g., KAPTON™) and conducting material (e.g., copper). The conducting material carries the electrical signals and the insulating material isolates the signal-carrying traces from each other. Alignment marks  401  can be an additional layer of copper bonded to the surface of insulating layer  408 , or can be part of an existing layer of material in flex circuit  407 . For example, alignment marks  401  can be applied to flex circuit  407  along with a copper ground plane, assuming that marks  401  are electrically isolated from the rest of the copper in the plane. For instance, the ground plane may stop short of the alignment markers and the end of the flex circuit to avoid shorting the transducers. Such a feature may provide for less expensive manufacturing of assembly  400 , since the alignment markers may be printed with the ground plane. Signal traces  402 , in this example, are of a pitch equal to that of alignment markers  401 ; however, the pitch of markers  401  may be a multiple or other ratio of the pitch of traces  402 . 
   A possible way to dice the acoustic stack and create individual transducer elements is to fabricate buss  404  to a very precise length, and then index a computerized saw blade from one end of buss  404 . The program controlling the saw then makes precise cuts at predetermined distances from the end. However, a disadvantage is that some amount of inaccuracy is typically present, especially when using only one end of buss  404  as an index. 
   A second possible way to dice the acoustic stack is to create kerfs  403  on surface  405  to guide the saw operator. Since alignment markers  401  are visible on surface  405  and are precisely placed to indicate the positions of traces  402 , a human or machine can make kerfs  403  aligned with markers  401  to indicate placement of dicing cuts. The acoustic stack may then be placed on surface  405  and diced according to kerfs  403 . In this way, a saw operator is ensured that such cuts will be placed between traces  402 , thereby creating a plurality of individual transducer elements. 
   In one example, kerfs  403  are only about two thousandths of an inch deep so that they make a mark in block  406  but do not sever buss  404 . During the final dice, the operator cuts through the acoustic stack and into backing block  406 , which, in this example, is enough to sever buss  404 , which is typically a few thousandths of an inch in depth. 
     FIG. 5  is an illustration of example flex circuit assembly  500  according to one embodiment of the invention.  FIG. 5  is a side view of assembly  500 , positioned such that buss  404  and signal traces  402  appear to the eye as a single, vertical component. Assembly  500  includes backing block  406 , buss  404 , traces  402 , and non-conducting layer  408 . In this example, the alignment markers are included on flap  501 . For instance, flap  501  includes alignment markers as vertical lines (not shown) that indicate the placement of signal traces  402 . Flap  501  protrudes from block  406  and can be bent outward and away from acoustic stack  502  during placement of acoustic stack  502 . This provides the dicing saw operator with one or more marks that are beyond the periphery of acoustic stack  502  and, therefore, visible at the time of dicing. The saw operator can then dice acoustic stack  502  according to the markers. It is possible that flap  501  may be trimmed off and removed after dicing, and may not be used for other processes in the assembly of the transducer. 
   Flap  501  may be made of a nonconductive material, such as KAPTON™, or may be made of copper or other materials as long as it does not interfere with the signal connections of the transducer array. In fact, flap  501  may be part of an existing KAPTON™ layer that is extended beyond block  406 . Alternatively, flap  501  may include thin pieces of copper extending beyond the KAPTON™, whereby the pieces of copper, themselves, act as the alignment markers. An advantage of some embodiments that use flaps is that the flaps take the place of scoring, thereby eliminating the step of making kerfs. 
     FIG. 6  is a flowchart of example method  600  for manufacturing a transducer device with flex circuit assembly  400  ( FIG. 4 ). In step  601 , a person or machine provides a cable with a flex circuit and a supporting block. The flex circuit includes a plurality of conductors terminating at a leading edge of the cable, and the plurality of conductors are placed upon a layer of insulating material, and a plurality of alignment markers are also placed upon the layer of insulating material at the leading edge. The plurality of alignment markers are electrically isolated from the plurality of conductors, and are, therefore, separate from the conductors. 
   The cable also includes a supporting block surrounding the flex circuit and exposing the leading edge of the flex circuit at a surface of the supporting block. Further, the plurality of alignment markers at the leading edge indicate positions of the plurality of conductors. Flex circuit assembly  401  of  FIG. 4  is suitable for use as the cable in step  601 . In such an embodiment, the plurality of conductors includes signal traces connected by a buss at the leading edge of the cable. 
   In step  602 , a person or machine scores the surface of the supporting block based on the alignment markers to produce kerfs that indicate the positions of the plurality of conductors. In one example, the kerfs are aligned with edges of the markers. In another example, the kerfs are aligned with the midpoints of the markers. The invention is not limited to any particular way of aligning kerfs with alignment markers, and any given way is within the scope of one or more embodiments. The kerfs extend toward the edge of the block sufficient to be visible after the acoustic stack is placed on the block. 
   In step  603 , a person or machine positions an electronic component on the surface of the supporting block so that the electronic component is in electrical communication with the plurality of conductors. In an example embodiment, an acoustic stack is placed on the surface so that it contacts the buss that connects the signal traces. In an embodiment that terminates signal traces without a buss, step  603  includes positioning the electronic device so that electrical connection is made with an adequate number of individual traces. 
   In step  604 , a person or machine dices the electronic component at one or more places, based upon the kerfs, to produce a plurality of separate transducer elements. In an embodiment wherein the kerfs are aligned with spaces between the conductors, dicing cuts may be made directly on the kerfs. In embodiments wherein the kerfs are aligned with the conductors, dicing cuts may be made between the kerfs, for example, at particular offsets from each kerf. When the flex circuit connects signal traces with a buss at the leading edge, step  604  may further include cutting through the buss to make electrically separate transducer elements. 
     FIG. 7  is a flowchart of example method  700  for manufacturing a transducer device with flex circuit assembly  500  ( FIG. 5 ). In step  701 , a person or machine provides a cable that includes a flex circuit. The flex circuit has a plurality of conductors terminating at a leading edge of the cable, and the plurality of conductors are placed on a layer of an insulating material. 
   The cable also includes a supporting block surrounding the flex circuit and exposing the leading edge at a surface of the supporting block. Further, the leading edge includes a structure that extends beyond the surface of the supporting block and has visual markings that indicate positions of the plurality of signal traces. Flex circuit assembly  500  ( FIG. 5 ) may be used as the cable of step  601 . 
   In step  702 , a person or machine positions an electronic component on the surface of the supporting block so that the structure is folded and the markings extend beyond the edges of the electronic component. In an example, an acoustic stack is placed on the supporting block, and the structure is a flap of KAPTON™ with alignment marks that is folded over. 
   In step  703 , based upon the markings, a person or machine dices the electronic component to produce a plurality of separate transducer elements, and each element is connected to at least one conductor of the plurality of conductors. In an example, a dicing saw operator aligns the saw with the markings on the part of the structure that extends beyond the acoustic stack. Then, the operator dices the stack as many times as necessary to produce a desired number of elements. 
   In step  704 , a person or machine removes a portion of the structure that extends beyond the edges of the electronic component. In an example embodiment, the flap of material with markings is not used for other purposes, and is removed by trimming in preparation for creation of a consumer or professional-grade finished product. 
   An advantage of some embodiments of the invention is that the shape of the alignment markers can be unique to the transducer, since the markers are not a part of the signal carrying circuitry. Therefore, a manufacturer typically will not have to take into account the effects of the markers on the signal-carrying properties of the transducer assembly. In fact, a manufacturer can design the markers any desirable way, keeping in mind the shape of the transducer, as the shape of the markers is not dependent on another function. Thus, some embodiments of the present invention allow for the separation of functions of markers and elements that affect performance, thereby permitting engineers to optimize each separately. 
   It should be noted that some manufacturers use computer programs to space out the dicing cuts of the acoustic elements in relation to features that have little relation to the acoustic performance of the product, for example, by using the edges of the backing block to index cuts. Various embodiments of the present invention may provide for more accuracy, since the markers are laid out in an alignment related to that of the traces. 
   Additionally, some embodiments are not limited to simply making cuts aligned between leads. For example, in some embodiments it might be desirable to place the leads off center while still making cuts along the entire length of the acoustic stack. Accordingly, alignment markers may be placed where necessary to guide the dicing saw operator. Therefore, in a general sense, some embodiments allow placing markers in any desirable pattern or placement. 
   Further, a manufacturer may use optical or electrical sensing machinery to recognize the markers and to place the kerfs and/or dicing cuts. For instance, machines may be able to detect the placement of markers made of conducting material (as in  FIG. 4 ) by deriving an electromagnetic signal from the markers. The markers may also be used to conduct signals if desired. For example, a machine may detect the markers when receiving the signal through contact. These features may permit the development of specialized machinery to recognize and follow alignment marks. 
   Various embodiments of the invention may improve the accuracy of dicing cuts above that provided by prior art dicing techniques. For example, basing dicing cuts on kerfs, such as those described with regard to  FIG. 4 , may result in fewer cut signal traces than the prior art technique of indexing from a side of the acoustic stack. Fewer cut traces leads to less waste and less cost to the manufacturer. 
   The examples above describe transducer arrays with a single row of elements. However, those of skill in the art will recognize that some embodiments may be adapted for use in systems that have multiple rows of elements. Further, the array may be straight or curved (concave or convex), depending on the application. 
   While the examples herein describe embodiments in the context of flex circuits in acoustic transducers, the invention is not so limited, as some embodiments may be adapted for use in systems that include optical, pressure, or other transducers. In fact, some embodiments may be adapted for use, more generally, in any kind of application that includes a plurality of small contacts on diced electrical components. For instance, a manufacturer may lay down a pattern of fine-conductor coaxial cables to make contact with a side of a transducer array. Then the manufacturer may make connections by, for example, soldering the cables to the transducer before it is diced. According to one embodiment of the invention, instead of relying upon the soldered connections, themselves, as guides for cutting, the manufacturer may add a secondary layer of alignment features that are not part of the signal-carrying circuit to indicate positions of the conductors. Examples of possible alignment features include lines on a sheet of insulating material and copper tabs that are laid down and insulated from a ground plane. 
   Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.