Patent Publication Number: US-8111480-B2

Title: Electronic component and tape head having a closure

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 11/036,148, filed Jan. 14, 2005 now U.S. Pat. No. 7,446,974, which is a divisional of U.S. patent application Ser. No. 10/346,033, filed Jan. 15, 2003 now U.S. Pat. No. 6,863,061. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to magnetic head fabrication, and more particularly, this invention relates to a method for reducing blade distortion during slicing of a wafer. 
     BACKGROUND OF THE INVENTION 
     Die separation, or dicing, by sawing is the process of cutting a thin film microelectronic substrate into its individual read/write recording devices with a rotating circular abrasive saw blade. This process has proven to be the most efficient and economical method in use today. It provides versatility in selection of depth and width (kerf) of cut, as well as selection of surface finish, and can be used to saw either partially or completely through a wafer or substrate. 
     Wafer dicing technology has progressed rapidly, and dicing is now a mandatory procedure in most front-end thin film packaging operations. It is used extensively for separation of die on thin film integrated circuit wafers. 
     Dicing thin film wafers by sawing is an abrasive machining process similar to grinding and cutoff operations that have been in use for decades. However, the size of the dicing blades used for die separation makes the process unique. Typically, the blade thickness ranges from 0.6 mils to 500 mils, and diamond particles (the hardest known material) are used as the abrasive material ingredient. Because of the diamond dicing blade&#39;s extreme fineness, compliance with a strict set of parameters is imperative, and even the slightest deviation from the norm could result in complete failure. 
     The diamond blade is a cutting tool in which each exposed diamond particle comprises a small cutting edge. Three basic types of dicing blades are available commercially: 
     Sintered Diamond Blade, in which diamond particles are fused into a soft metal such as brass or copper, or incorporated by means of a powdered metallurgical process. 
     Plated Diamond Blade, in which diamond particles are held in a nickel bond produced by an electroplating process. 
     Resinoid Diamond Blade, in which diamond particles are held in a resin bond to create a homogeneous matrix. 
     Thin film wafer dicing is dominated by the plated diamond blade, which has proved most successful for this application. 
     Increasing use of more expensive and exotic materials, coupled with the fact that they are often combined to produce multiple layers of dissimilar materials, adds further to the dicing problems. The high cost of these substrates, together with the value of the circuits fabricated on them, makes it difficult to accept anything less than high yield at the die-separation phase. 
     Thin film wafers are of a standardized size, and thus, the number of die that can be cut from each wafer is limited. To maximize the amount of wafer space that can be used for circuitry, and thus the die yield per wafer, the area cut away during slicing must be minimized. This can be accomplished only by using thinner blades and by elimination of yield loss due to deviation of the blade from the desired cut path. 
     One category of component created by thin film processing is the tape head. Many heads (such as hard disk recording heads and some tape heads) do not use closures, so they are relatively easy to slice. However, most conventional tape heads use closures.  FIG. 1  depicts one such tape head  100 . The head  100  consists of a pair of head portions  102 , each having a closure  104  that engages the tape  106  as it passes over the head  100 . 
     For those heads that use closures, a problem arises during slicing by state of the art methods. To maximize yield, the cut is made through the wafer  202  such that it shaves off one edge of the closure  104 . See  FIG. 2 . Because the blade engages more material on one side of the blade than the other, the blade becomes distorted, causing the blade to stray from the desired cut path and destroy die. 
     Cutting the wafer along side the closure rather than through the edge of the closure is not desirable for cutting rows from the wafer because of the typically high margin of error during sawing. By moving the saw path closer to the circuitry, the blade is more likely cut into the read/write circuitry, rendering the die unusable. The only remedy under this traditional method of cutting would be to increase the size of each row on the wafer to compensate for blade deviation or to accommodate a thicker blade. Either way, the end result would be an undesirable decrease in yield. 
       FIG. 3  depicts a prior art attempt at reducing blade distortion. As shown, a stiffener  300  is coupled to the non-wafer-contacting portion of the blade  200  to add to the resiliency of the blade  200 . While this solution does remedy blade distortion to a degree, it does not eliminate the yield loss completely, as some distortion still occurs, with the resulting deviation from the cut path and circuit destruction. 
     It would be desirable to achieve the aforementioned benefits using conventional, and therefore, less expensive blades. It would also be desirable to use a thinner blade to allow a higher yield per wafer. It would also be desirable to decrease the error rate caused by deviation of the blade during sawing 
     SUMMARY OF THE INVENTION 
     An electronic component, comprising: a portion of a row cut from a wafer; and a closure coupled to the portion of the row of the wafer towards a first edge of the portion of the row of the wafer; the portion of the row of the wafer having a bonding area positioned adjacent a second edge of the portion of the row of the wafer, the second edge of the portion of the row of the wafer being positioned opposite the first edge of the portion of the row of the wafer and along a same side thereof, wherein the bonding area includes a layer of adhesive thereon. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a fuller understanding of the nature and advantages of the present invention, as well as the preferred mode of use, reference should be made to the following detailed description read in conjunction with the accompanying drawings. 
         FIG. 1  is a side view of a tape head having closures. 
         FIG. 2  is a side view of a prior art cutting process illustrating distortion of the blade. 
         FIG. 3  is a side view of a prior art cutting process in which the blade has been reinforced to reduce blade distortion. 
         FIG. 4  is a perspective view of a section of a thin film wafer according to one embodiment. 
         FIG. 5  is a perspective view of an array of closures. 
         FIG. 6  is a perspective view depicting coupling of the array of closures to the section of wafer. 
         FIG. 7  is a perspective view of the array of closures coupled to the section of wafer. 
         FIG. 8  is a perspective view of the closures coupled to the section of wafer upon removing a top portion of the array. 
         FIG. 9  is a side view depicting cutting of a row from a section of wafer. 
         FIG. 10  is a side view of a row cut from a wafer. 
         FIG. 11  is a perspective view of a row cut from a wafer. 
         FIG. 12  is a perspective view of a dice cut from a row. 
         FIG. 13  is a perspective view of a dice coupled to a U-beam. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     The following description is the best embodiment presently contemplated for carrying out the present invention. This description is made for the purpose of illustrating the general principles of the present invention and is not meant to limit the inventive concepts claimed herein. 
     The present invention provides a method and mechanism for slicing a thin film wafer to form such things as tape head components. A thin film wafer can be any type of composite or composition capable of containing circuitry therein, and includes semiconductor wafers. 
     According to the preferred method, the thin film wafer is cut into rectangular sections, sometimes called quads.  FIG. 4  illustrates a section  400  of a thin film wafer according to one embodiment. As shown, the section  400  includes a plurality of rows  402  of circuitry that will eventually be sliced and diced to form die. Each row  402  can contain multiple read and/or write elements. 
       FIG. 5  shows an array  500  of closures  502  that will be bonded to a section  400  of the wafer.  FIG. 6  illustrates how the array  500  is bonded to a section  400 . 
       FIG. 7  depicts the array  500  of closures  502  bonded to the section  400  of wafer. The portions of the closure  502  remaining after processing support the tape as the tape slides over the head to protect the delicate electronics in the head from wear, similar to the way the tape  106  engages the head  100  shown in  FIG. 1 . 
     A top portion  504  of the array  500  of closures  502  may be removed prior to slicing the section  400  into rows  402 . See  FIG. 5 . Grinding may be used to remove the top portion  504  of the array  500 .  FIG. 8  shows the closure  502  and section  400  with the top portion  504  of the array  500  of closures  502  removed. 
     As shown in  FIG. 9 , a blade  900  is used to slice rows from each section  400  by cutting through the closure  502  and section  400  such that opposite sides of the blade  900  engage an equal surface area of the closure  502 . In other words, the blade  900  fully engages the closure  502 . 
     One way to ensure that blade  900  engages equal surface areas of the closure  502  is to increase the size of the closure  502  such that the closure  502  overlaps the kerf completely. For example, if sawing is performed with a 120 micron blade  900 , the closure  502  should cover about a 125 micron kerf (120 micron cutting width plus 5 microns to allow for deviation). The excess amount of closure can be removed later, as discussed below. 
     Another way is to use a very thin blade  900  that fully engages the closure  502 . The cutting width of the blade is less than the width of the closure, where the width of the closure is defined opposite sides of the closure that are oriented generally parallel to the rotational plane of the blade. Preferably, the cutting width of the blade is less than three quarters (75%), and ideally less than one half (50%), the width of the closure. The cutting width of the blade  900  is preferably less than 150 microns, more preferably less than 100 microns, and ideally less than 75 microns. The closure  502  actually aids the blade  900  in keeping its shape because the amount of material on each side of the blade  900  is the same. 
       FIG. 10  illustrates a row sliced from the section  400 . Upon slicing, two pieces of closure material remain coupled to the row. One portion  1000  of the closure material is desired and will function to engage the tape when the row is placed in a tape head. The other portion  1002  of the closure material, referred to as a sliver  1002 , is removed. The sliver  1002  can be removed by lapping. For example, the sliver  1002  may be removed during the back-lap process, which laps the sawed edge to smooth it. 
     The sliver  1002  can be removed mechanically, i.e., by some physical mechanism, without removing material from the row. One example would be by using human labor and an implement such as tweezers. Optionally, the row  402  can be thermally treated for at least temporarily affecting properties of an adhesive bonding the sliver  1002  onto the row  402  for assisting removal of the sliver  1002 . For example, depending on the type of adhesive used to bond the closure  502  to the wafer, the temperature of the row  402  can be reduced to make the adhesive become temporarily brittle, and thereby make the sliver  1002  easier to remove. For example, if adhesive becomes brittle at temperatures below −60° C., the temperature of the row  402  can be reduced to below −60° C. prior to removing the sliver  1002 . 
       FIG. 11  shows a row after the sliver  1002  is removed. The rows are then diced into individual thin film elements, or die  1200 , using traditional methods. See  FIG. 12 , which illustrates one dice  1200 . Each dice  1200  is coupled to a U-beam  1300 , as shown in  FIG. 13 . The U-beams  1300  are eventually coupled together to form a head. 
     In use, the thin film elements created by the process and instruments described herein can be used in magnetic recording heads for any type of magnetic media, including but not limited to disk media, magnetic tape, etc. 
     While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. For example, the structures and methodologies presented herein are generic in their application to all types of thin film devices. Thus, the breadth and scope of a preferred embodiment should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.