Patent Publication Number: US-2022234166-A1

Title: Methods of lapping while heating one or more features, and related sliders, row bars, and systems

Description:
RELATED APPLICATION 
     This application is a divisional patent application of application Ser. No. 16/434,853 filed on Jun. 7, 2019, which in turn claims the benefit of commonly owned provisional Application having Ser. No. 62/686,433, filed on Jun. 18, 2018, wherein each of said patent applications are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND 
     The present disclosure relates to systems and methods of lapping a slider and/or row bar of sliders that can ultimately be used in a hard disc drive for read/write operations. 
     SUMMARY 
     The present disclosure includes embodiments of a method of lapping a row bar having a plurality of sliders, wherein the method comprises: 
     a) providing the row bar having a plurality of sliders, wherein at least one slider comprises a transducer region comprising: at least a first magnetoresistive element and a second magnetoresistive element, wherein the first magnetoresistive element has a first feature that has a first distance from a first target value in the lapping direction and the second magnetoresistive element has a second feature that has a second distance from a second target value in the lapping direction, wherein the first distance minus the second distance is equal to a delta distance; and 
     b) applying a current to an element in the transducer region to generate heat and cause at least the first magnetoresistive element to expand in the lapping direction relative to the second magnetoresistive element, wherein the current is controlled to cause the first magnetoresistive element to expand in the lapping direction an amount equal to the delta distance; and 
     c) lapping the row bar while applying the current. 
     The present disclosure also includes embodiments of a row bar having a plurality of sliders, wherein at least one slider comprises a transducer region, wherein the transducer region comprises: 
     a) a magnetoresistive writer element; 
     b) a magnetoresistive reader element; 
     c) at least one electrical resistance heating element and/or at least one thermal sensor located proximal to the magnetoresistive reader element and/or the magnetoresistive writer element; 
     d) a first row of a plurality of electrical contact pads; and 
     e) a second row of a plurality of electrical contact pads, wherein the first row of electrical contact pads extends along a downtrack direction at a first position in a lapping direction, wherein the second row of electrical contact pads extends along the downtrack direction at a second position in the lapping direction, wherein the at least one electrical resistance heating element and/or at least one thermal sensor is electrically coupled to at least one electrical contact pad in the second row, and wherein the at least one electrical contact pad in the second row is electrically coupled to at least one electrical contact pad in the first row. 
     The present disclosure also includes embodiments of a lapping system comprising: 
     a) a carrier structure; 
     b) the row bar of claim  16 , wherein the row bar is removably mounted to the carrier, wherein the carrier structure has a mechanical actuator that is configured to physically contact the row bar and actuate a slider in the lapping direction; and 
     c) a lapping plate having a lapping surface that is operable to rotate and contact the row bar for lapping the first magnetoresistive element and the second magnetoresistive element. 
     The present disclosure also includes embodiments of a row bar having a plurality of sliders, wherein at least one slider comprises a transducer region, wherein the transducer region comprises: 
     a) a magnetoresistive writer element; 
     b) a first electrical resistance heating element located proximal to the magnetoresistive writer element; 
     c) a magnetoresistive reader element; 
     d) a second electrical resistance heating element located proximal to the magnetoresistive reader element; and 
     e) a third electrical resistance heating element located proximal to the magnetoresistive writer element or the magnetoresistive reader element. 
     The present disclosure also includes embodiments of a lapping system comprising: 
     a) a carrier structure; 
     b) the row bar of claim  18 , wherein the row bar is removably mounted to the carrier, wherein the carrier structure has a mechanical actuator that is configured to physically contact the row bar and actuate a slider in the lapping direction; and 
     c) a lapping plate having a lapping surface that is operable to rotate and contact the row bar for lapping the first magnetoresistive element and the second magnetoresistive element. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  shows a schematic, cross-section view of a portion of a slider in a row bar that can be lapped according to the present disclosure; 
         FIG. 1B  shows a schematic, cross-section view of a portion of the magnetoresistive writer element  105  shown in  FIG. 1A ; 
         FIG. 1C  shows a schematic, cross-section view of a portion of the magnetoresistive reader element  110  shown in  FIG. 1A ; 
         FIG. 1D  shows a schematic, cross-section view of the portion of the slider shown in  FIG. 1A  when the writer electrical resistive heater  125  is energized; 
         FIG. 1E  shows a schematic, bottom view of the portion of the slider shown in  FIG. 1D ; 
         FIG. 1F  shows a schematic, cross-section view of the portion of the slider shown in  FIG. 1D  after the slider has been lapped; 
         FIG. 1G  shows a schematic, cross-section view of the portion of the slider shown in  FIG. 1E  when the writer electrical resistive heater  125  is no longer energized; and 
         FIG. 2  is a schematic, cross-section view of a portion of the slider shown in  FIG. 1A  that includes electrical contact pads. 
     
    
    
     DETAILED DESCRIPTION 
     A magnetic recording apparatus can be referred to as a hard disk drive (HDD) and includes a slider that flies above a disk by using air as a lubricant (an “air bearing”). For example, a disk can be placed on a spindle motor that can rotate and a negative pressure air-lubricated bearing slider can be attached at a suspension to correspond to the magnetic disk. The negative pressure air-lubricated bearing slider can be moved by an actuator that pivots so that the slider moves to a desired position on a track of the disk. The disk used as a recording medium has a circular shape and different information can be recorded on each track. In general, to obtain desired information, the slider moves in search of a corresponding track on the disk. The disk can have a magnetic layer that is susceptible to physical and/or chemical damage. To help mitigate such damage, such a disc often has a coating such as Diamond-like Carbon (DLC) as an overcoat to help protect the magnetic layer from physically and/or chemically induced damage. 
     A lapping tool is used for machining a surface of a row bar that can be later sliced into a plurality of individual sliders. The lapping tool can have a rotating lapping plate defining a lapping surface which can help abrade the surface of a slider. If desired, a slurry can be applied to the lapping surface to enhance the abrading action as the lapping surface is rotated relative to a row bar containing a plurality of the sliders held in a pressing engagement against the lapping surface. Lapping a row bar of sliders permits multiple slider bodies to be processed together, which can advantageously be relatively simple, precise and/or cost-effective. Lapping can involve multiple lapping steps such as rough lapping and final (kiss) lapping. At a desired point in manufacturing, individual sliders can be sliced from the row bar and ultimately used in a hard disk drive. 
     Rough Lapping can be considered a relatively coarse lapping procedure used to remove relatively more material as compared to kiss lapping. For example, rough lapping can remove up to 10 micrometers of material from a row bar in the lapping direction, or even up to 20 micrometers of material from a row bar in the lapping direction. A row bar can be tilted at a specific position relative to the lapping plate to target a particular element (e.g., reader or writer). 
     Kiss Lapping can be considered a fine lapping procedure and can be used to remove fractions of material from a row bar as compared to rough lapping. For example, kiss lapping can remove 0.5 microns or less, or even 0.1 microns or less of material from a row bar in the lapping direction. 
     After rough lapping, but before kiss lapping, two or more electronic features in the transducer region of a given slider may be at different distances from their target values in the lapping direction. For example, before kiss lapping, a magnetoresistive writer element (also referred to as a “writer”) may be at a different distance from its target value as compared to a magnetoresistive reader element (also referred to as a “reader”), thereby creating a delta distance (also referred to as a reader/writer delta). Lapping to each target value of a writer and reader during kiss lapping can be difficult when a reader/writer delta is present. 
     According to the present disclosure, a heat source in the transducer region of a slider can be used to selectively expand an electronic feature (e.g., a writer) relative to another feature (e.g., a reader) within a given slider so that the expanded portion can be removed, thereby reducing or eliminating the delta distance. For example, a writer could be expanded an amount in the lapping direction equal to the reader/writer delta so that that amount could be removed via lapping, thereby removing the reader/writer delta. 
     The present disclosure can be applied to a variety of slider heads such as perpendicular magnetoresistive (PMR) heads, head-assisted magnetoresistive (HAMR) heads, and the like. In some embodiments, the present disclosure can be especially useful with respect to PMR heads because the accuracy of the write pole width can be very desirable, especially as the write pole width is reduced and the flare angle is increased. 
     Embodiments of the present disclosure can include a row bar having a plurality of sliders. At least one slider includes a transducer region. The transducer region includes at least a first magnetoresistive element and a second magnetoresistive element. The first magnetoresistive element has a first feature that has a first distance from a first target value in the lapping direction. The second magnetoresistive element has a second feature that has a second distance from a second target value in the lapping direction. The first distance minus the second distance is equal to a delta distance. In some embodiments, a similar relationship among every first magnetoresistive element and second magnetoresistive element is present in every slider in the row bar. That is, every slider in a row bar includes at least a first magnetoresistive element and a second magnetoresistive element. The first magnetoresistive element in each slider has a first feature that is a first distance from a first target value in the lapping direction. The second magnetoresistive element in each slider has a second feature that is a second distance from a second target value in the lapping direction. And the first distance minus the second distance is equal to a delta distance. The delta distance may be the same or different among individual sliders. 
     In more detail, for illustration purposes, an embodiment according to the present disclosure is described with respect to  FIGS. 1A-1G  where the first magnetoresistive element is a magnetoresistive writer element (writer) and the second magnetoresistive element is a magnetoresistive reader element (reader). 
     As used herein, the direction along x-axis (into the page of  FIG. 1A ) is referred to as the cross-track axis. The direction along the z-axis is referred to herein as the down-track axis, with reference to trailing edge  156 . The direction along the y-axis is referred herein as the lapping direction (direction of material removal) or the reader stripe height direction and writer break-point direction. 
     As shown in  FIG. 1A , one slider  111  of a plurality of sliders in row bar  100  is illustrated. Slider  111  includes a transducer region  101  having at least a magnetoresistive writer element  105  and a magnetoresistive reader element  110 . In some embodiments, a row bar according to the present disclosure can include at least 30 sliders, at least 60 sliders, or even at least 70 sliders. A slider according to the present disclosure can be mostly made out of ceramic material. As shown in  FIG. 1A  slider  111  includes an “AlTiC break”  150 . The area  151  to the right of break  150 , the bulk of the material is alumina titanium-carbide (also referred to as AlTiC). The area  152  to the left of break  150 , the bulk of the material, with the exception of many of the features in the transducer region  101 , is alumina. Elements such as magnetoresistive writer element  105  are made of magnetic materials such cobalt-iron (CoFe), nickel-iron (NiFe), and the like. 
     As shown in  FIG. 1B , the magnetoresistive writer element  105  has a write pole  106  as a first feature that has a first distance  108  from a writer break point target position  109  as a first target value in the lapping direction. The writer break point distance  107  coincides with the writer break point target position  109  at the air bearing surface  162  after material is removed in the lapping direction by an amount represented by first distance  108 . 
     As shown in  FIG. 1C , the magnetoresistive reader element  110  has a reader stripe height  113  as a second feature that has a second distance  112  from a reader stripe height target position  114  as a second target value in the lapping direction. The reader stripe height  113  coincides with the reader stripe height target position  114  at the air bearing surface  162  after material is removed in the lapping direction by an amount represented by second distance  112 . 
     Referring back  FIG. 1A , as can be seen, there is a difference (delta)  120  between first distance  108  and second distance  112 . That is, the distance  108  of the magnetoresistive writer element  105  from its writer break point target position  109  is different than the distance  112  of the magnetoresistive reader element  110  from its reader stripe height target position  114 , thereby creating delta distance  120 . 
     In some embodiments, the delta distance  120  is 50 nanometers or less. For example, delta distance  120  can be in the range from 0.1 nanometers to 40 nanometers, from 0.5 nanometers to 40 nanometers, or from 0.1 nanometers to 10 nanometers. 
     As explained above, according to the present disclosure, a heat source in the transducer region of a slider can be used to selectively expand an electronic feature (e.g., a writer) relative to another feature (e.g., a reader) within a given slider so that the expanded portion can be removed, thereby reducing or eliminating the delta distance  120 . 
     Heat can be generated from a variety of electrical elements present in a transducer region of a slider. In some embodiments, the electrical element in the transducer region can be chosen from an electrical resistive heater, writer coils of a magnetoresistive write element, a laser/near field transducer (on-wafer laser), and combinations thereof. 
     As shown in  FIG. 1 , examples of electrical resistive heaters include one or more of writer electrical resistive heater  125  and reader electrical resistive heater  126 . Writer electrical resistive heater  125  is located proximal to magnetoresistive writer element  105  and reader electrical resistive heater  126  is located proximal to magnetoresistive reader element  110 . Writer electrical resistive heater  125  and/or reader electrical resistive heater  126  are examples of electrical resistive heaters that can be used during lapping according to present disclosure and during operation of a hard disc drive to adjust the distance between the writer and/or reader, respectively, and an underlying rotating disc. 
     In some embodiments, one or more optional electrical resistive heaters can be included that are dedicated to lapping operations. The one or more optional electrical resistive heaters can be located proximal to the feature that they are intended to selectively expand in the lapping direction. As shown in  FIG. 1 , the transducer region  101  includes an optional electrical resistive heater  128  that is also located proximal to magnetoresistive writer element  105 . In use during lapping, as described below, the optional electrical resistance heating element  128  can be energized during lapping to cause the magnetoresistive writer element  105  to selectively expand relative to the magnetoresistive reader element  110  by an amount equal to delta distance  120 , while the electrical resistance element  125  is not energized during lapping. In use during hard disc drive operation, the optional electrical resistance heating element  128  is not energized, but the electrical resistance element  125  can be energized to adjust the distance between the magnetoresistive writer element  105  and an underlying rotating disc (not shown). 
     Electrical resistive heaters (e.g.,  125 ,  126 , and  128 ) can be placed proximal to a magnetoresistive element so that it causes the magnetoresistive element to thermally expand in the “y” direction relative to another magnetoresistive element in the slider by a desired amount. For example, if writer electrical resistive heater  125  is energized to generate heat, it can cause the magnetoresistive writer element  105  to expand a first distance in the “y” direction. Further, when the writer electrical resistive heater  125  is energized to generate heat, it can also cause the magnetoresistive reader element  110  to expand a second distance in the “y” direction depending on the location of the writer electrical resistive heater  125  in the downtrack “z” direction. The ratio of the first distance to the second distance can be referred to as “gamma.” In some embodiments in can be desirable to locate an electrical resistive heater (e.g.,  125 ) proximal to its associated magnetoresistive element (e.g.,  105 ) so that “gamma” is relatively high so that, e.g., writer electrical resistive heater  125  causes little to no expansion of the magnetoresistive reader element  110  in the “y” direction. In some embodiments, an electrical resistive heater (e.g., writer electrical resistive heater  125 ) is proximally located to its associated magnetoresistive element (e.g., magnetoresistive writer element  105 ) so that the heater is from 0.5 to 5 micrometers in the downtrack direction from the magnetoresistive element. In some embodiments, energizing an on-wafer-laser can be a desirable element to energize during lapping because it can relatively localize the heat that is generated thereby producing a relatively high and desirable “gamma.” 
     In some embodiments, an electrical resistive heater can be located above the air bearing surface in the lapping direction “y” by a distance in the range from 1 to 10 micrometers. 
     In some embodiments, two or more sliders  111  in the row bar  100  have delta distances  120 . In some embodiments, all sliders  111  in the row bar  100  have delta distances  120 . Two or more delta distances  120  within a row bar  100  can have delta distances that are different from each other. In such cases, as described below, the present disclosure can apply an appropriate heat source to each individual slider to create a corresponding expansion by the appropriate delta distance in the lapping direction to remove the expanded material during lapping, thereby reducing or eliminating the delta distance among features within a given slider. 
     Embodiments of the present disclosure include applying a current to an element in the transducer region to generate heat and cause at least a first magnetoresistive element to expand in the lapping direction relative to at least a second magnetoresistive element. The current can be controlled to cause the first magnetoresistive element to heat up and expand in the lapping direction by an amount equal to the delta distance. The coefficient of thermal expansion of each of the different areas or elements within the area being heated can be taken into account when determining how much current to apply to the element that generates heat. 
     An example of applying current to an element to cause an area to heat up and selectively expand during lapping is described with respect to  FIGS. 1D-1G . The slider in  FIG. 1A  represents a slider  111  that has been through rough lapping.  FIGS. 1D-1G  represent various points in a kiss lapping process. Referring to  FIG. 1D , a pre-determined current is applied to an element  125  in the transducer region  101  to generate heat and cause at least the first magnetoresistive element  105  to expand in the lapping direction relative to the second magnetoresistive element  110 . The current can be adjusted and controlled to cause the first magnetoresistive element  105  to expand in the lapping direction an amount equal to the delta distance  132 , which corresponds to delta distance  120  in  FIG. 1A . As shown in  FIG. 1D , delta distance  132  is the distance between reference line  130  and reference line  131 . Reference line  130  is coplanar with air bearing surface  162 . The amount of current to cause protrusion  132  can be determined from the heat generated from the element due to resistance heating and the coefficient of thermal expansion of the area that is heated. For example, referring to  FIGS. 1D and 1E , an amount of current is applied to heater  125  to cause the area  117  to expand in the lapping direction “y” toward lapping plate  160 . The coefficient of thermal expansion of the area  117  is taken into account to determine how much current to apply to heater  125  to expand magnetoresistive writer element  105  by a distance  132 . 
     The row bar  111  can be caused to contact the rotating surface  161  of lapping plate  160  so that the expanded portion of the slider  111  can be removed, as shown in  FIG. 1F , while applying the current. As also shown in  FIG. 1F , the slider  111  has been lapped to planarize slider  111  so that the ABS  162  corresponds to the reader stripe height target position  114  of the magnetoresistive reader element  110 . As shown in  FIG. 1G , when the current is stopped so no heat is generated via heater  125 , the area  117  cools down and recedes so that magnetoresistive writer element  105  recedes in the lapping direction “y” by a distance equal to delta distance  120 . Thus, the air bearing surface  162  at the magnetoresistive writer element  105  now coincides with the writer break point target position  109 . Accordingly, a degree of freedom can be introduced into the lapping process (e.g., kiss lapping process) by heating an element such as electrical resistance element  125 . In some embodiments, a current can be applied to every slider in a row bar to cause the magnetoresistive writer element  105  in each slider  111  to expand in the lapping direction by an amount corresponding to the delta  120  of each slider  111 . Thus, for every electrical resistance element  125  used during lapping as described above the same number of degrees of freedom can be introduced for that row bar  100 . In some embodiments, a lapping system can connect a wire to the writer electrical resistive heater  125  on every head of every slider  111 . Current can flow down one slider and up an adjacent slider, and any remaining current imbalance can be handled by a ground pad connection on first and last (dummy) sliders on every row bar. 
     In some embodiments, the one or more elements in each slider that are selected to electrically generate heat as described herein can be the only elements in the slider that are energized with current during lapping. For example, with respect to  FIG. 1A , the writer electrical resistive heater  125  can be the only element in slider  111  that is energized with current during lapping while current is not applied to, e.g., the magnetoresistive writer element  105  and the magnetoresistive reader element  110  during lapping. As another example, the writer electrical resistive heater  125  and/or the writer coil of magnetoresistive writer element  105  can be energized with current to generate heat while current is not applied to, e.g., the magnetoresistive reader element  110  during lapping. 
     As described above, one or more sliders  111  in a row bar  100  can have a delta distance  120  that is different from a delta distance in one or more other sliders  111  in the row bar. As one example, each slider  111  in a row bar  100  could have a delta distance  120  that is different from the delta distance  120  in every other slider in the row bar  100 . Because the delta distance  120  can vary among sliders in a row bar, the current that is applied to each individual heat generating element in each slider  111  (e.g., writer electrical resistive heater  125 ) can be different from the current applied to every other individual heat generating element in each corresponding slider  111  (e.g., writer electrical resistive heater  125 ). 
     In some embodiments, controlling kiss lapping to writer break point target position  109  can be performed with writer electrical resistive heater  125  and controlling kiss lapping to reader stripe height target position  114  can simultaneously be performed with an actuator arm of a mounting carrier. Examples of lapping carriers are described in U.S. Pat. No. 9,776,299 (Herendeen) and U.S. Pub. No. 2015/0258655 (Koon et al.), wherein the entireties of said patent documents are incorporated herein by reference. In some embodiments, controlling lapping to writer break point target position  109  and reader stripe height target position  114  can be performed in this manner for each slider  111  of a row bar. This corresponds to two degrees of freedom of lapping control for each slider  111 . For example, if a row bar has 68 sliders, then using a writer electrical resistive heater and carrier actuator for the magnetoresistive writer element  105  and the magnetoresistive reader element  110 , respectively, of each slider as described herein can provide at least 136 degrees of freedom for lapping control. 
     In some embodiments, before kiss lapping as described herein with respect to  FIGS. 1A-1G , a magnetoresistive element such as magnetoresistive writer element  105  can be intentionally underlapped from the writer break point target position  109 . In some embodiments, one or more magnetoresistive elements can be underlapped in the lapping direction by a distance from 0.5 to 10 nanometers. This can facilitate using a heat source according to the present disclosure to cause relative expansion among magnetoresistive elements and avoid overlapping the magnetoresistive element that is underlapped. 
     A variety of alternatives can be configured according to the present disclosure. For example, the reader electrical resistive heater  126  could be energized during lapping instead of writer electrical resistive heater  125 . This way, the magnetoresistive reader element  110  could be caused to expand due to the heat generated by reader electrical resistive heater  126 . Simultaneously and in conjunction, a carrier actuator could be used to physically actuate the slider  111  and control the writer break point target position  109  of magnetoresistive writer element  105 . 
     In some embodiments, one or more electronic lapping guides (ELGs) can be used during lapping. An ELG has an electrical resistance that can change as conditions change. For example, the electrical resistance of an ELG can increase as ELG material is removed during a lapping process and thus may be used to monitor lapping of the air bearing surface  162  during slider  111  manufacturing. Accordingly, an ELG may be formed in a slider and the ELG resistance may be monitored during lapping. The resistance of an ELG can be correlated to material removed from an element that the ELG is associated with such as magnetoresistive writer element  105 , magnetoresistive reader element  110 , and/or a near-field transducer (not shown). Thus, the ELG can be used to target a desired dimension of the magnetoresistive writer element  105 , the magnetoresistive reader element  110 , and/or a near-field transducer. For example, an ELG can be used during lapping to target a height value for the magnetoresistive reader element  110  (e.g. reader stripe height target position  114 ) and another ELG can be used during lapping to target a height value for the magnetoresistive writer element  105  (e.g., writer break point target position  109 ). ELGs are also described in U.S. patent documents 7,551,406 (Thomas et al.), U.S. Pat. No. 7,643,250 (Araki et al.), U.S. Pat. No. 8,165,709 (Rudy), 2006/0168798 (Naka), and 2010/0208391 (Gokemeijer), wherein there entireties of said patent documents are incorporated herein by reference. 
     As shown in  FIG. 1E , slider  111  includes a writer ELG  115  and a reader ELG  116 . Writer ELG  115  and reader ELG can each be located hundreds of microns away in the cross-track direction “x” from magnetoresistive writer element  105  and magnetoresistive reader element  110 , respectively. During lapping, if writer electrical resistive heater  125  is used as described herein to expand slider  111  in the area  117  (“heat bubble”), then the writer ELG  115  can likewise be hundreds of microns outside of area  117 . If the writer ELG  115  is located outside the area  117 , then the writer ELG  115  may not provide the intended metrology with respect to magnetoresistive writer element  105  while magnetoresistive writer element  105  is expanding as shown in  FIG. 1D . In some embodiments, one or thermal sensors can be located proximal (e.g., within area  117 ) to a given element being expanded (e.g., magnetoresistive writer element  105 ). Advantageously, a thermal sensor can provide desirable metrology information with respect to an element during lapping while the element is expanded due to heating. For example, a thermal sensor  127  can be located proximal to magnetoresistive writer element  105  within area  117 . In some embodiments, a thermal sensor can be located within 0.5 to 5 micrometers in the downtrack “z” direction of its associated magnetoresistive element. A the thermal sensor can be located above the final air bearing surface in the lapping direction such that material is not removed from the thermal sensor during lapping as is the case with its associated magnetoresistive element. In some embodiments, a thermal sensor can be located above the air bearing surface in the lapping direction “y” by a distance in the range from 0.1 to 1 micrometers. 
     During lapping, while current is applied to writer electrical resistive heater  125  and heating area  117 , the resistance of thermal sensor  127  can be measured. Temperature can be inferred from the measured resistance of thermal sensor  127 . Then, the inferred temperature can be used to calculate the corresponding protrusion of magnetoresistive writer element  105  from a model that correlates temperature to protrusion of magnetoresistive writer element  105 . 
     A non-limiting example of correlating temperature to protrusion of magnetoresistive writer element  105  is described herein below. A thermal sensor such as sensor  127  can be a thin sheet of resistive metal that can be used determine resistance vs temperature for the thermal sensor  127  either empirically or using a look-up table. An empirical approach can include raising and/or lowering the ambient temperature and measuring the resistance change of the sensor  127  in a row bar  100  as a function of temperature. Using a look-up table can include obtaining literature values from a look-up table for resistance change vs temperature for the material(s) used in this thermal sensor  127 . 
     Also, a model for heater current or power vs temperature can be used. This can involve electrically connecting to a heater in a slider (e.g., a reader heater, a writer heater, or a dedicated lapping heater) and electrically connecting to a thermal sensor (e.g., sensor  127 ) in the slider. Next, the current or power delivered to the heater can be varied and the resistance of the thermal sensor  127  measured. Finally, the heater current or power can be plotted versus the resistance of thermal sensor  127 . It is noted that this calibration method can be done while not lapping, because lapping may remove material from the thermal sensor and cause resistance to change. Also, calibration can be done with a row bar in contact with a static (non-rotating) lapping plate or without a row bar in contact with a lapping plate. 
     Finally, correlating temperature to protrusion of magnetoresistive writer element  105  can include a model for temperature vs protrusion of a writer or reader. Commercially available software packages are available like COMSOL Multiphysics® software that can be used to model the protrusion profiles of a writer or reader while an electrical heater is used at different power settings. Empirical modeling can be performed by electrically connecting to a heater, lapping bars under under a range of heater currents/powers, and then measuring the height profiles for a reader and a writer protrusion using either an atomic force microscope or with an optical profilometer 
     One non-limiting example of a thermal sensor  127  is referred to as a dual-ended temperature coefficient of resistance sensor (DETCR). An example of a DETCR is described in U.S. Pat. No. 8,638,349 (Liu et al.), wherein the entirety of said patent document is incorporated herein by reference. Another non-limiting example of a thermal sensor  127  includes a thermal asperity detector (TAD). An example of a TAD is described in U.S. Pub. No. 2003/0065992 (Yang), wherein the entirety of said patent document is incorporated herein by reference. 
     In some embodiments, the temperature of a row bar  111  can unintentionally fluctuate due to one or more factors such as frictional heating due to lapping, the temperature of the surrounding environment. Such fluctuations may cause the elements that are heated to expand (e.g., e.g., the magnetoresistive writer element  105  and the magnetoresistive reader element  110 ) more or less than intended. Also, such fluctuations in temperature can increase or decrease the resistance detected in an ELG, which can indicate an incorrect amount of material that is lapped away from the ELG and corresponding element. A lapping plate having a temperature control system can help control the temperature of the a row bar in physical contact with the lapping place so as to reduce or substantially eliminate such temperature fluctuations. An example of such a temperature control system is described in patent application titled “A LAPPING SYSTEM THAT INCLUDES A LAPPING PLATE TEMPERATURE CONTROL SYSTEM, AND RELATED METHODS” by Habermas et al. having application No. 62/686,417 filed on Jun. 18, 2018, wherein the entirety of said patent application is incorporated herein by reference. 
     In order to electronically access slider elements (e.g., magnetoresistive writer element  105 , etc.), a slider can include a plurality of electrical contact pads that may be electrically connected to the slider elements.  FIG. 2  is a schematic that shows the trailing edge face  157  of slider  111 . The contact pads illustrated are present on the trailing edge face.  FIG. 2  also includes an electrical wiring diagram showing how the contact pads are electrically connected to devices such as ELGs, writer heater, DETCR. and the like. As shown in  FIG. 2 , slider  111  includes a first row  205  of electrical contact pads along the cross track axis “x” and a second row  220  of electrical contact pads along the cross track axis “x”. The first row  205  of contact pads include a ground contact pad  208  and can be electrically connected to features used during head-gimbal assembly (HGA) operation in a hard disk drive (HDD). The second row  220  of electrical contact pads can be dedicated for use of features used during lapping according to the present disclosure. That way, electrical connections can be made to the second row  220  of electrical contact pads and then after lapping is done, the second row  220  of electrical contact pads can just be left unused, thereby leaving the first row  205  of electrical contact pads in relatively good condition. For example, the first row  205  of electrical contact pads can avoid having undue scratching or any remnants of wire bonds from the lapping process. 
     In more detail, with reference to the slider  111  illustrated in  FIGS. 1A-1G , electrical contact pads  206  and  207  can be electrically connected to magnetoresistive writer element  105  and electrical contact pads  211  and  212  can be electrically connected to magnetoresistive reader element  110 . Reader electrical resistive heater  126  can be electrically connected to electrical contact pad  213 . 
     With respect to the slider  111  elements used during lapping as described herein, writer ELG  115  can be electrically connected to electrical contact pads  222  and  223  and reader ELG  116  can be electrically connected to electrical contact pads  221  and  222 . Advantageously, writer ELG  115  and reader ELG  116  can share a common electrical contact pad  222  to save space in the second row  220  of electrical contact pads. 
     Also, thermal sensor  127  (e.g., DETCR) can be electrically connected to electrical contact pads  225  and  226  in the second row  220 , which can be electrically connected to electrical contact pads  209  and  210 , respectively, in the first row  205 . Finally, writer electrical resistive heater  125  can be electrically connected to electrical contact pad  224  in the second row  220  and electrical contact pad  214  in the first row  205 . This way, electrical connections can be made to electrical contact pads in the second row  220  for lapping purposes, thereby avoiding undue scratching and/or remnants of wire bonds on electrical contact pads in the first row  205 . 
     Electrical contact pads can be made out a variety of conductive materials such as gold and the like. Elements can be electrically connected to contact pads via bonding, soldering, or other electrical connection. For example, gold wire can be used to electrically connect a contact pad to an element.