Abstract:
The present disclosure relates to a method, to distribute a solder-reinforced adhesive on a first substrate ( 110 ), comprising (i) positioning the first substrate ( 110 ) to receive an adhesive composite ( 250 ) including, an adhesive ( 200 ) and a plurality of solder balls ( 300 ) on a first contact surface ( 115 ) of the first substrate ( 110 ), (ii) applying, by a distribution nozzle ( 205 ), on the first contact surface ( 115 ), the adhesive composite ( 250 ), and (iii) distributing, by a conductive spreader ( 520 ), the adhesive composite ( 250 ). The present disclosure further relates to a method to determine electrical resistance of an solder-reinforced adhesive between a first substrate ( 110 ) and a second substrate ( 120 ), comprising (i) applying, by a distribution nozzle ( 205 ), on a first contact surface ( 115 ) of the first substrate ( 110 ), an adhesive composite ( 250 ) including, an adhesive ( 200 ) and a plurality of solder balls ( 300 ), (ii) positioning, to a portion of the adhesive composite ( 250 ) opposite the first contact surface ( 115 ), a second contact surface ( 125 ) of the second substrate ( 120 ), (iii) attaching, to the first substrate ( 110 ) and the second substrate ( 120 ), at least one electrical resistance detector ( 550 ), and (iv) applying, to the first substrate ( 110 ) and the second substrate ( 120 ), an electrical current.

Description:
TECHNICAL FIELD 
       [0001]    The present technology relates to adhesive bonding for substrate materials. More specifically, the technology provides reinforced adhesive bonding in various ways through the use of solder balls. 
       BACKGROUND 
       [0002]    Structural adhesives replace welds and mechanical fasteners in many applications because structural adhesives reduce fatigue and failure commonly found around welds and fasteners. Structural adhesives can also be preferable to welds and mechanical fasteners where resistance to flex and vibration is desired. 
         [0003]    Adhesive bonding uses structural adhesives to connect a substrate surface of one material to another substrate surface of the same material or a different material. Adhesive bonding is widely used in applications in which materials with low bonding temperature are required or in applications requiring the absence of electric voltage and current. Additionally, adhesive bonding may help improve corrosion resistance through eliminating substrate material contact with fasteners and other corrosive elements. 
         [0004]    When structural adhesives are applied to substrate surfaces, a bond line forms at the meeting of the substrate surfaces. Uniformity within the bond line is an important factor for optimal adhesive performance, thus dictating that bond line thickness is critical in designing a bond joint. 
         [0005]    When substantial force exists, structural adhesives used in adhesive bonding may be loaded (1) normal to the bond line, which creates a peeling effect causing substrate materials to be on different planes (i.e., peel fracture), or (2) perpendicular to the leading edge of a fracture, whether in-plane or out-of-plane, which creates a shearing effect where substrate materials remain on the same plane (i.e., shear fracture). While fracturing is typically avoided, if there is to be fracturing, shear fracture is preferred over peel fracture because shear fracture requires an external loading that is greater than that of peel fracture to produce failure. 
         [0006]    Adhesives by nature exhibit fluid-like characteristics for tacking substrates during bonding processes and solid characteristics (often known as cured adhesives) for sustaining load in a finished assembly. Curing of an adhesive can be either a process of physical transformation and/or chemical transformation that occurs during a definite period of time when physical or chemical energy exchange occurs within the adhesive or between the adhesive and the environment. During the period of energy exchange, external forces are required to hold the substrates and adhesive together before the adhesive cures and gains strength. 
         [0007]    Unlike in a welded joint where metallic alloy bonds form between the substrates, a cured adhesive holds the substrates together via electro-static or van der Waals forces at the adhesive-substrate interfaces and polymer bonds within the adhesive. Since bonds within adhesive joints may become unstable when subject to activation energy levels, adhesive joints are often complemented by welding and mechanical fasteners to achieve long term stability. 
         [0008]    Resistive spot welding (RSW), a process, prior to curing, in which metal substrates are joined by heat from an electric current after the substrates are assembled with an adhesive. RSW can be used to promote structural stability between substrates during handling of an adhesive-bonded assembly, curing of the adhesive to gain bond strength, as well as during the use of the finished product. The amount of heat (energy) delivered to the spot is determined by the resistance between the electrodes and the magnitude and duration of the current. The heat required to fuse bond metals (e.g., steel and aluminum) can result in a high temperature that causes evaporation of the adhesive or chemical degradation of the adhesive. 
       SUMMARY 
       [0009]    A need exists for a structural adhesive that creates bond line uniformity and provides sufficient strength and stability during subsequent processing and usage. The present disclosure relates to systems and methods for establishing a structural adhesive that creates bond line uniformity and provides strength and dimensional stability until the structural adhesive cures during subsequent processing. Additionally, the present disclosure relates to methods to provide in-line process monitoring of the structural adhesive bondline. 
         [0010]    In one aspect, the present technology includes a method to distribute a solder-reinforced adhesive on a first substrate, comprising (i) applying an adhesive using a first distribution nozzle on a first contact surface of a first substrate, (ii) applying a plurality of solder balls using a second distribution nozzle, such that at least one of the plurality of solder balls is within the adhesive, and (iii) distributing the plurality of solder balls by a conductive spreader, such that at least one of the plurality of solder balls is in contact with the first contact surface. 
         [0011]    In another aspect, the present technology includes a method to distribute a solder-reinforced adhesive on a first substrate, comprising (i) positioning, the first substrate to receive an adhesive composite including, an adhesive and a plurality of solder balls on a first contact surface of the first substrate, (ii) applying, by a distribution nozzle, on the first contact surface, the adhesive composite, and distributing, by a conductive spreader, the adhesive composite, such that at least one of the plurality of solder balls is in contact with the first contact surface, and (iii) distributing, by a conductive spreader, the adhesive composite, such that at least one of the plurality of solder balls is in contact with the first contact surface. 
         [0012]    In some embodiments, the conductive spreader traverses a bond line in a direction normal to the first contact surface to distribute the plurality of solder balls throughout the adhesive. 
         [0013]    In some embodiments, a nozzle controller measures electrical resistance difference between the conductive spreader and the first substrate through the adhesive composite. 
         [0014]    In some embodiments, the method further comprises, identifying a bondline by a nozzle controller associated with the conductive spreader. 
         [0015]    In further embodiments, the method further comprising, verifying a fault condition within the bond line using the nozzle controller associated with the conductive spreader, and communicating the fault condition to a system external of the distribution nozzle by the nozzle controller. 
         [0016]    In yet another aspect, the present technology includes a method to determine electrical resistance of an solder-reinforced adhesive between a first substrate and a second substrate, comprising (i) applying, by a distribution nozzle, on a first contact surface of the first substrate, an adhesive composite including an adhesive and a plurality of solder balls, distributed by a conductive spreader such that at least one of the plurality of solder balls is in contact with the first contact surface, (ii) positioning, to a portion of the adhesive composite opposite the first contact surface, a second contact surface of the second substrate, and (iii) attaching, to the first substrate and the second substrate, at least one electrical resistance detector, energized by an energy storage element, and (iv) applying, to the first substrate and the second substrate, an electrical current such that each of the plurality of solder balls creates an electrical resistance. 
         [0017]    In some embodiments, the method comprises, comparing, the electrical resistance to a predetermined electrical resistance value stored by a resistance controller. 
         [0018]    In some embodiments, the method further comprises, applying heat to the first substrate such that the at least one solder ball reaches the solder-ball bonding temperature. 
         [0019]    In some embodiments, the method further comprises, applying, to the first substrate and the second substrate, the electrical current such that each of the plurality of solder balls creates an electrical resistance. 
         [0020]    In some embodiments, the method further comprises, comparing, the electrical resistance to a predetermined electrical resistance value stored by a resistance controller. 
         [0021]    In some embodiments, the method further comprises, applying, to the first substrate and the second substrate, the electrical current such that each of the plurality of solder balls creates an electrical resistance. 
         [0022]    Other aspects of the present technology will be in part apparent and in part pointed out hereinafter. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  illustrates a side view of a bonding system with solder balls concentrated under a localized heating element. 
           [0024]      FIG. 2  illustrates a side view of a bonding system with solder balls distributed throughout the bondline. 
           [0025]      FIG. 3  illustrates an exploded perspective view of the exemplary embodiment of  FIG. 2  containing solder balls with a random distribution and a localized heating element. 
           [0026]      FIG. 4  is a flow chart a flow chart illustrating methods associated with a distribution sequence and resistance sequence. 
           [0027]      FIG. 5  illustrates an exemplary embodiment of distribution sequence in  FIG. 4 . 
           [0028]      FIG. 6  illustrates an exemplary embodiment of resistance sequence in  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    As required, detailed embodiments of the present disclosure are disclosed herein. The disclosed embodiments are merely examples that may be embodied in various and alternative forms, and combinations thereof. As used herein, for example, exemplary, illustrative, and similar terms, refer expansively to embodiments that serve as an illustration, specimen, model or pattern. 
         [0030]    Descriptions are to be considered broadly, within the spirit of the description. For example, references to connections between any two parts herein are intended to encompass the two parts being connected directly or indirectly to each other. As another example, a single component described herein, such as in connection with one or more functions, is to be interpreted to cover embodiments in which more than one component is used instead to perform the function(s). And vice versa—i.e., descriptions of multiple components described herein in connection with one or more functions are to be interpreted to cover embodiments in which a single component performs the function(s). 
         [0031]    In some instances, well-known components, systems, materials, or methods have not been described in detail in order to avoid obscuring the present disclosure. Specific structural and functional details disclosed herein are therefore not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present disclosure. 
         [0032]    While the present technology is described primarily in connection with manufacturing components of a vehicle in the form of an automobile, it is contemplated that the technology can be implemented in connection with manufacturing components of other vehicles, such as marine craft and air craft, and non-vehicle apparatus. 
         [0033]    I. Bonding System 
         [0034]    Now turning to the figures, and specifically to the first figure,  FIG. 1  illustrates a bonding system identified by reference numeral  100 . The bonding system  100  includes a structural adhesive  200  and solder balls  300  which are used to join a first substrate  110  to a second substrate  120 . 
         [0035]    The substrates  110 ,  120  are the materials that require bonding to one another. The substrates  110 ,  120  may be composed of the same or differing material compositions. Typical substrate material may include materials such as aluminum, steel, magnesium, composite, ceramic, or the like. 
         [0036]    The adhesive  200  is a structural material used to bond a contact surface  115  of the first substrate  110  to a contact surface  125  of the second substrate  120 . The adhesive  200  forms a bond line  210  between the contact surfaces  115 ,  125 . In  FIGS. 1 and 2 , the bond line  210  extends laterally between the substrates  110 ,  120  and has a thickness  212 . 
         [0037]    In the present disclosure, the thickness  212  is approximately between about 0.05 to about 0.3 millimeters (mm). As an example, if the contact surfaces  115 ,  125  are relatively flat, the bond line  210  may have a thickness  212  of approximately 0.2 mm to allow for optimal shear and tensile strength. 
         [0038]    In  FIG. 1 , the solder balls  300 ,distributed in a defined area,have the ability to bond to one or both of the substrates  110 ,  120  in the defined area prior to and during manufacturing process (e.g., a curing process). Following the close of the substrates  110 ,  120  with adhesive  200  between the contacting surfaces  115 ,  125 , the solder balls  300  serve to hold the system  100  together before formation of an adhesive bond in a curing process, for example. 
         [0039]    In  FIG. 2 , incorporating solder balls  300  within a majority of the adhesive  200  also improves fracture resistance of a bond joining the substrates  110 ,  120 . As an example, a fracture threshold in an adhesive without solder balls may occur approximately near 1.8 N/mm, whereas the same fracture in adhesive containing solder balls may occur at approximately near 11.5 N/mm. 
         [0040]    The embodiments and the examples provided herein illustrate and describe the solder balls  300  as spherical in shape, which promotes uniform distribution of the solder balls  300  from adjacent solder balls  300  within the defined area or throughout the adhesive  200 . However, the solder balls  300  may include other shapes such as, but not limited, to cylinders, rectangles, and the like. 
         [0041]    The solder balls  300  can vary in size, shape, and dimension within the system  100 . The solder balls  300  should allow contact between at least one of the solder balls and both of the substrates  110 ,  120  under an applied pressure on either or both substrates  110 ,  120 . For example, if the bond line  210  has a thickness  212  of 0.2 mm, the solder balls  300  may have a dimension of approximately near 0.2 mm or larger, to ensure compression of the solder balls  300  during bonding, which will ensure adequate joining to contact surfaces  115 ,  125 . 
         [0042]    The solder balls  300  may be composed of any commercially available material or a custom composition. When at least one of the substrates  110 , 120  is at least partially composed of metal and/or metal composites, composition materials of the solder balls  300  may include materials such as tin (Sn), lead (Pb), silver (Au), copper (Cu), zinc (Zn), bismuth (Bi), and/or the like. If at least one of the substrates  110 , 120  is at least partially composed of polymer and/or polymer composites, the solder ball  300  composition may also include polymer materials such as polycarbonate (PC), polyethylene (PE), polypropylene (PP), divinylbenzene (DVB), and/or the like. 
         [0043]    In some embodiments, bonding of the solder balls  300  to substrates  110 ,  120  prior to curing of adhesive  200  may be performed using a spot heating element  400  (seen in  FIG. 3 ). Bonding of the solder balls  300  to the substrates  110 ,  120  allows the structure and dimensionality of the bondline  212  to maintain its integrity until the adhesive  200  cures during a subsequent operation (e.g., paint). 
         [0044]    The heat element  400  can be a localized, heating element used to bond the solder balls  300  to one or both contact surfaces  115 ,  125 . The heat element may be approximately in contact with one or both substrates  110 ,  120 . The heat element  400  can be used to conduct spot soldering for a specific period of time at a temperature conducive for bonding. For example, the spot soldering can occur when the heat element is greater than 200° C. for a short duration of time (e.g., 2 to 5 seconds). 
         [0045]    The heat element  400  may include flat or textured and include one or more round or square face(s) in the order of 1 to 500 mm 2 . The tip of the heat element  400  may be constructed with any material that is thermally conductive and can sustain temperature up to 300° C. or above. 
         [0046]    In some embodiments, the heat element  400  may be a one-piece tool with a surface transmitting heat toward either substrate  110  or  120 , whichever is in contact with the heat element  400 . The one-piece heat element  400  may also serve as a compression tool to compress the second substrate  120  against the adhesive  200  and solder balls  300 , which compresses against the first substrate  120 , or vice versa. When used as a compression tool, the heat element  400  causes the solder balls  300  to ensure contact and bonding with the contact surface  115 ,  125 . 
         [0047]    In some embodiments, the heat element  400  may be in the form of two electrical electrodes, at opposite potentials,in contact with both substrates  110 ,  120  from opposing directions. The substrates  110 ,  120  and solder balls  300 , each having an electrical conductivity, generate enough heat to form spot solders between the substrates  110  and  120 , which provides the substrates  110 ,  120  enough bond force to maintain the dimensionality of the substrates  110 ,  120  until the adhesive  200  cures during subsequent processing. The two electrical electrodes may also serve as compression tools acting together to compress the system  100 , so that the solder balls  300  may bond to the contact surface  115 ,  125 . 
         [0048]    Desirable characteristics of the solder ball  300  include, but are not limited to (1) a density conducive for bonding, (2) a temperature conducive for bonding, and (3) increased tensile strength over prior art. 
         [0049]    The density should be such that the solder balls maintain their structure when incorporated into the adhesive  200  prior to bonding. The solder balls  300  density can be approximately between about 0.5 and about 15.00 g/cm 3 . For example, a solder ball containing tin-lead (Sn—Pb) or tin-silver-copper (Sb—Ag—Cu or SAC) may have a density approximately near 7.5 g/cm 3 , which may provide adequate density for bonding when at least one of the substrates  110 , 120  is at least partially composed of metal and/or metal composites. As another example, a solder ball containing ethenylbenzene or divinylbenzene (DVB) may have a density approximately near 0.9 g/cm 3 . 
         [0050]    The temperature should be such that the solder balls  300  bond without affecting (e.g., deforming) composition materials of the substrate  110 ,  120 . In some embodiments it is desirable to include a solder ball that has a melting point of less than 200° C. to prevent de-bonding (e.g., fracture) of the solder balls  300  from the contact surfaces  115 ,  125  and improve fracture resistance of the adhesive  200 . 
         [0051]    In some embodiments, the solder balls  300  can be composed of materials that are high in strength and bond at a high temperature (e.g., above 200° C.). High temperature solder balls  300  are melted in spot soldering prior to adhesive curing to secure dimensions of the substrates  110 ,  120  during adhesive curing cycle. These high temperature solder balls are used in the example shown in  FIG. 1  where solder balls are located in specific areas that are spot soldered. 
         [0052]    In some embodiments, the solder balls  300  can be bonded at a low temperature (e.g., below 200° C.). Low temperature spot soldering maintains structure and dimensionality of the system  100 while the adhesive  200  strengthens during curing. As the temperature rises during curing, the solder balls  300 , including those previously spot soldered, melt and bond with one or both of the substrates  110 ,  120 . When the temperature reduces (e.g., returns to ambient temperature), solder bonds are formed throughout the bondline  212  where the solder balls  300  contact at least one of substrates  110  and  120 . 
         [0053]    In some embodiments, the solder balls  300  may be composed of materials that include different bonding temperatures below and above 200° C. Using a combination of high temperature and low temperature solder balls  300 , allows the low and high temperature solder balls  300  under the heat element  400  to bond during spot soldering while allowing low temperature solder balls to bond during the adhesive curing process in other locations within the bondline  212 . 
         [0054]    Tensile strength of the system  100 ,as measured under tension forces,should be greater when compared to an adhesive without filler material or an adhesive containing non-bonding filler material. For example, when solder balls  300  are used in conjunction with the adhesive  200 , the overall system  100  may have a tensile strength of approximately between about 50 MPa and 150 MPa, whereas an automotive adhesive alone may have a tensile strength of approximately between about 15 MPa and 35 MPa, and an automotive adhesive with glass beads may have a tensile strength of approximately between about 15 MPa and 35 MPa. 
         [0055]    In some embodiments, the bond line thickness  212  is such that the solder balls  300  may join to both of the contact surfaces  115 ,  125  (seen in  FIG. 1 ). Joining the solder balls  300  to both contact surfaces  115 ,  125  has benefits including promoting a crack that propagates in the adhesive  200  approximately near solder balls  300  according to a fracture path that requires the greatest amount of fracture energy (i.e., the amount of energy required to propagate the crack). The crack may (i) propagate along a pre-identified fracture path  222  (depicted as a series of short solid arrows in  FIG. 1 ), (ii) propagate along a pre-identified fracture path  224  (depicted as a series of dashed arrows in  FIG. 1 ), (iii) propagate along a pre-identified fracture path  226  (depicted as a series of long solid arrows in  FIG. 1 ), or (iv) arrest at the interface of the adhesive  200  and the solder ball  300 . 
         [0056]    The fracture paths  222 ,  224 ,  226  correlate generally to a path of greatest resistance for any fracture. Because the adhesive  200  is generally weaker than the substrates  110 ,  120  and the solder balls  300 , the fracture paths may extend through the adhesive  200  as illustrated by the fracture paths  222 ,  224  or along one of the contact surfaces as illustrated by the fracture path  226 . 
         [0057]    When the crack propagates around each solder ball  300 , the fracture path  222  is formed along one of contact surfaces  115 ,  125 , as shown in  FIG. 1 . Although  FIG. 1  depicts the fracture path  222  extending around each solder ball  300  toward the first contact surface  115 , alternatively, the fracture path  222  could extend around any one or more of the balls  300  toward the second contact surface  125 . Although  FIG. 1  depicts the fracture path as continuing around each subsequent solder ball  300 , in actuality, when the fracture path  222  approaches each subsequent solder ball  300 , the fracture path  222  may (i) travel around the solder ball  300 , (ii) travel through the solder ball  300 , (iii) travel along one of the contact surface  115 ,  125 , or (iv) arrest at the interface of the adhesive  200  and the solder ball  300 . 
         [0058]    The fracture path  224  is formed when a crack propagates through the solder ball  300  and then propagates into the adhesive  200  prior to reaching a subsequent solder ball  300 . Similar to the fracture path  222 , when the fracture path  224 , reaches each subsequent solder ball  300 , the fracture path  224  may (i) travel around the solder ball  300 , (ii) travel through the solder ball  300 , or (iii) travel along one of the contact surface  115 ,  125 , or (iv) arrest at the interface of the adhesive  200  and the solder ball  300 . 
         [0059]    The fracture path  226  is formed when a crack propagates around the solder ball  300  and along one of the contact surfaces  115 , 125 . Unlike the fracture paths  222 ,  224 , when the fracture path  226  is formed, the crack continues to propagate along the contact surface  115 ,  125  where the crack commenced. 
         [0060]    Alternately, the crack may arrest at any interface of the adhesive  200  as the solder ball  300  along the paths  222 ,  224 ,  226 . Arresting of the crack may be highly desired within the system  100  because reduced or eliminated propagation of the crack may prevent failure of the system  100  due to fracture. 
         [0061]    In some embodiments, the bond line thickness  212  is such that the solder balls  300  join to only one of the contact surfaces  115 ,  125 . A benefit of restricting solder ball  300  contact to one contact surface  115  or  125  is the ability to join dissimilar substrate materials (e.g., metal material joining with a composite material—e.g., polymer composite) without compromising the integrity of either substrates  110 ,  120 . 
         [0062]    Where the first substrate  110  has a different composition than the second substrate  120 , bonding the substrates  110 ,  120  according to the present technology may have an added benefit of enhanced strength at the bond line  210  compared to prior art. Specifically, e.g., the bond line  210  is stronger with the incorporation of solder balls  300  because the energy required to initiate fracture path propagation around the solder balls  300  is higher than the energy required for fracture path propagation in the adhesive alone or along an adhesive/metal interface. 
         [0063]    II. Method of Performing Uniform Distribution— FIGS. 4 and 6  (P027926) 
         [0064]    In some embodiments, the solder balls  300  are contained in the adhesive  200  and are dispensed out of a distribution nozzle  205 . The dispensing of the solder balls  300  can be monitored according to a sequence  400 , which can be monitored with the use of electric conduction, as seen in  FIG. 4 . A spreading and dispense monitoring method for adhesive and solder balls includes a distribution sequence  401  and an electrical resistance sequence  402 . The solder balls  300 , composed of materials with electrical conductance, can be electrically conducted to ensure proper contact with the substrates  110  and/or  120 , which have another electrical conductance. 
         [0065]    In some embodiments, the solder balls  300  are positioned within the adhesive  200  after the adhesive  200  is dispensed out of the nozzle  205  onto the contact surface  115  of the first substrate  110 . The positioning of the solder balls  300  can be monitored according to a sequence  400 , which can be monitored with the use of electric conduction, as seen in  FIG. 4 . The method includes a distribution sequence  401  and an electrical resistance sequence  402 . The solder balls  300 , composed of materials with electrical conductance, can be electrically conducted to ensure proper contact with the substrates  110  and/or  120 , which an electrical conductance different from the adhesive  200 . 
         [0066]    For example, the sequence can be accomplished by a robotic dispensing system. The dispensing system can include a controller  207 , discussed below, to monitor inlet and outlet valves for accurate deposition and control of material flow. The dispensing systems can be designed to accurately and quickly dispense the adhesive  200  and the solder balls  300  for application such as, but not limited to,bonding. The dispensing system together can store, using a memory, or the like, dispensing programs created and quickly programs to start a production cycle. Within each dispensing program, the adhesive  200  can be applied at different flow rates to ensure, for example, proper flow of the adhesive  200 . 
         [0067]    The distribution sequence  401  begins at step  405  with positioning the first substrate  110  to receive the adhesive  200  alone or an adhesive composite  250  including the adhesive  200  and the solder balls  300 . 
         [0068]    Next, at step  410 , an energy storage element  510 is attached to the first substrate  110  as well as a conductive spreader  520  as seen in  FIG. 5 . 
         [0069]    The storage element  510 , can be any conventional storage device known in the art, such as but not limited to capacitor, battery, or the like. The storage element  510  should be able to store enough energy to operate the components (e.g., conductive spreader  520 ) associated with measuring electrical resistance in the system  100 . 
         [0070]    Next, at step  415 , the energy storage element  510  is activated. When the element  510  is activated, electrical current flows through the element  510  to the first substrate  110  and the conductive spatula  520 . 
         [0071]    In some embodiments, the storage element  510 , can be an activated through a controller  502  containing a processor (not shown). 
         [0072]    The controller  502  may be a microcontroller, microprocessor, programmable logic controller (PLC), complex programmable logic device (CPLD), field-programmable gate array (FPGA), or the like. The controller may be developed through the use of code libraries, static analysis tools, software, hardware, firmware, or the like. Any use of hardware or firmware includes a degree of flexibility and high-performance available from an FPGA, combining the benefits of single-purpose and general-purpose systems. After reading this description, it will become apparent to a person skilled in the relevant art how to implement the technology using other computer systems and/or computer architectures. 
         [0073]    The controller  502 may include structure such as, but not limited to, processors, data ports, memory with categories of software and data used in the energy storage  510 , and the like. 
         [0074]    Next, at step  420 , a distribution nozzle  205 , seen in  FIG. 5 , is energized. When the nozzle  205  is energized the adhesive composite  250  is allowed to flow onto the first contact surface  115  of the first substrate  110 . 
         [0075]    The nozzle  205  can include any conventional nozzle suitable for distribution of the adhesive composite  250 . For example, the nozzle  205  can be a portion of a robotic adhesive application. Such a robotic application can include a controller equipped with a processor (not shown) to monitor inlet and outlet valves for accurate deposition and control of material flow. 
         [0076]    In some embodiments, the distribution nozzle  205  includes a controller  207 . The controller  207  can be of similar structure and function as the controller  502 . 
         [0077]    Next, at step,  430 , the applicator determines if a fault condition exists. Fault condition can include, for example, adhesive composite  250  flowing improperly, or not at all, from the nozzle  205 . If the adhesive composite  250  is not flowing (e.g., path  422 ), the sequence may display an indicator at step  440 . The indicator can be any alert, such as but not limited to warnings, displays, alarms or the like, which are communicated to the robotic application or an operator. 
         [0078]    As another example, a fault condition can include a scenario where an insufficient amount of solder balls  300  are present within the adhesive  200 . If an insufficient amount of solder balls  300  is present (e.g., path  422 ), the sequence may display an indicator at step  440 . 
         [0079]    A sufficient amount of solder balls  300  may be determined when the electrical resistance is determined at step  465  below. Indicators can also include reset switches to reactive detectors  550  once the fault condition has been corrected. Additionally, a reset switch to reactivate detectors once fault condition (e.g., adhesive distribution) has been corrected. 
         [0080]    If no faults are detected (e.g., path  424 ), the adhesive composite  250  is smoothed using the conductive spreader  520  at step  450 . 
         [0081]    The conductive spreader  520  contains an electric charge from the energy storage element  510 , which creates and applies pressure and electrical conductance to the composite mixture which sends electrical conductance through the solder balls  300 . The conductive spatula  520  only needs to apply enough electricity and pressure to the adhesive composite  250 to ensure sufficient contact between the adhesive composite  250  and the first substrate  110  to retain and properly spread the adhesive composite  250  on the first substrate  110 . 
         [0082]    The electrical resistance sequence beings at step  455  with positioning the second substrate  120  on top of the composite of adhesive  200  and solder balls  300 . 
         [0083]    Next, at step  460 , one or more resistance detectors  550 , is attached to the both substrates  110  and  120 , as seen in  FIG. 6 . 
         [0084]    The detectors  550  can be positioned on an outer edge of the substrates  110 ,  120  to cause an in-line electrical resistance  570  through the first substrate  110 , through the solder ball  300  (by-passing the non-conductive adhesive  200 ), and finally aligned with the second substrate  120 . 
         [0085]    Next, at step  465 , the electrical resistance  270  generated between the detectors  550  is measured. When the detectors  550  are in positioned and electrical resistance  570  is passed through the system  100 , detect value of electrical resistance as an indicator of the degree of solder bonding to both substrates  110 ,  120 . Additionally, the detectors  550  that can work as spot soldering or resistance spot welding electrodes. 
         [0086]    Next, at step  470 , the sequence  402  determines if the electrical resistance is sufficient for the particular application.  FIG. 5  illustrates three areas, which are scanned by the detectors  550  to determine electrical resistance  570  within the scanned area. Area (1) illustrates a solder ball  300  joined to both substrates  110 ,  120 ; area (2) illustrates a solder ball  300  bonded to only one substrate, specifically, substrate  120  in  FIG. 4 ;and area (3) illustrates no solder ball or an insufficient amount of adhesive. 
         [0087]    In area (1), the solder ball  300  has a bond with both substrates  110 ,  120 , which will provide a level of electrical resistance. In area (2), the scanned area the solder ball  300  only has a bond with the first substrate  110 , which will provide a larger level of electrical resistance than scenario (1). In area (3), the solder ball  300  does not include a solder ball  300 , which will provide no electrical resistance because no current is present. 
         [0088]    In some embodiments, it is desirable to have the minimum resistance provided within scanned area. However, a higher level of resistance may be acceptable in particular situation (e.g., when the substrates  110  and  120  are composed of different materials). 
         [0089]    If one or more of the scanned area does not meet the desired electrical resistance (e.g., path  472 ), the sequence  400  may display an indicator after scanning areas (2) and/or (3) an indicator can be displayed at step  440 . A lack of solder bonds or adhesive bonding can cause inferior bond strength, therefore as a means to repair, the same electrical resistance detecting electrodes may be used to establish a resistance spot weld by increasing pressure applied on the substrates  110 ,  120  by the electrodes and passing through a large amount of electrical current between the substrates  110 ,  120 . 
         [0090]    If the scanned areas meet the desired electrical resistance (e.g., path  474 ), the sequence  400  passes the scanned area to a future stage within the manufacturing process (e.g., curing) at step  480 . 
         [0091]    III. Conclusion 
         [0092]    Various embodiments of the present disclosure are disclosed herein. The disclosed embodiments are merely examples that may be embodied in various and alternative forms, and combinations thereof. 
         [0093]    The above-described embodiments are merely exemplary illustrations of implementations set forth for a clear understanding of the principles of the disclosure. 
         [0094]    Variations, modifications, and combinations may be made to the above-described embodiments without departing from the scope of the claims. All such variations, modifications, and combinations are included herein by the scope of this disclosure and the following claims.