Abstract:
A chip slapper is presented, having a substrate, a conductive layer disposed above the substrate face, and an intermediate layer disposed between the substrate face and the conductive layer. The conductive layer and intermediate layer form a first land and a second land atop the substrate face, with a bridge formed of the intermediate layer spanning between the first land and the second land. A first adhesion portion is attached to the first land, and a second adhesion portion is attached to the second land, wherein at least a portion of the bridge is not overlaid by the first adhesion portion or the second adhesion portion.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/147,206, filed Apr. 14, 2015, entitled “Device and Method for a Detonator with Improved Polyimide Adhesion,” which is incorporated by reference herein in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to explosives, and more particularly, is related to a detonator device. 
       BACKGROUND OF THE INVENTION 
       [0003]    Slapper type detonators in general cause a “flying plate” or “flyer layer” to be propelled at a high velocity against a secondary explosive medium creating a shock wave which results in the detonation of the secondary explosive. In a typical design, there are two wide area conductive lands separated by a narrow rectangular bridge member. The lands are connected to a capacitor through a high voltage switch. When the switch closes, the capacitor provides current across the lands which vaporizes the bridge member turning it into a plasma. This plasma accelerates a portion of the dielectric material covering the bridge member, the flying plate or flyer layer, to a high velocity, causing the flying plate or flyer layer to slap into an explosive. The resulting shock wave causes detonation of the explosive. This type of detonator is also known as a “chip slapper detonator.” 
         [0004]      FIGS. 1 through 3  show diagrams illustrating the production process for a prior art chip slapper. In  FIGS. 1 through 3  the thickness of the relative layers are exaggerated for the purposes of illustration. 
         [0005]    Manufacturing may begin with a wafer  60 ,  FIG. 1  which includes a ceramic substrate layer  62 , a sticking layer  64 , for example, titanium tungsten, a first conductive layer  66 , for example, copper, a buffer layer  68 , and a second conductive layer  70 , for example, a gold coating. The buffer layer  68  may be, for example, a titanium-tungsten composition. The buffer layer  68  may retard or prevent inter-diffusion between copper of the first conductive layer  66  and the second conductive layer  70 . Similarly, forming the second conductive layer  70  of gold may promote solder-ability of land areas  42 ,  44  ( FIG. 2 ). 
         [0006]    The wafer  60  may be used to fabricate one or more chip slappers  46 . First, for each chip slapper  46 , the second conductive layer  70 , the buffer layer  68 , the copper conductive layer  66 , and the sticking layer  64  may be etched as shown in  FIG. 2  to form wide land areas (lands)  42  and  44  and a narrow bridge portion  50  spanning between the lands  42 ,  44 . In  FIG. 2 , only one chip slapper  46  is shown but it is to be understood that wafer  60 , ( FIG. 1 ) may be used to produce a number of chip slappers  46  as shown in  FIG. 2 . 
         [0007]    After the lands  42 ,  44  and the bridge  50  have been etched, the second conductive layer  70  is etched off the bridge portion  50  to expose buffer material  68  as shown in  FIG. 3 . A non-conductive flyer layer, for example, a dielectric coating such as polyimide or Kapton® layer,  52  is secured to the bridge portion  50  of each chip slapper  46 . Each individual chip slapper  46  may be cut from the wafer  60  ( FIG. 1 ). 
         [0008]    Thus, the chip slapper  46  includes a substrate  54  formed of the ceramic substrate layer  62 , the sticking layer  64  on the substrate  54 , the conductive layer  66  on the sticking layer  64  in the shape of lands  42  and  44  separated by a bridge portion  50  between the lands  42  and  44 . In alternative embodiments, the substrate  54  may be formed of other materials, for example, sapphire, silicon nitride, synthetic diamond, beryllium, or silicon with an oxide layer on top, among others. 
         [0009]    The bridge  50  is formed from an exposed portion of the buffer layer  68 , and disposed upon the conductive layer  66 . The second conductive layer  70  is disposed over the buffer layer  68 . The second conductive layer  70 , as explained above, typically extends across and forms an exposed surface of at least a substantial portion of the lands  42  and  44 , but may be absent from all or a substantial portion of the bridge portion  50 . The flyer layer  52  is then placed over the bridge portion  50 . The buffer material  68  acts to prevents migration of the second conductive layer  70  into the material of the conductive layer  66  and vice versa. The buffer material  68  also acts to better adhere the flyer layer  52  on bridge portion  50  where the second conductive layer  70  is absent. 
         [0010]      FIG. 4A  is a top view of the diagram of  FIG. 3  with the flyer layer  52  removed for clarity.  FIG. 4B  is a top view similar to  FIG. 4A  with the flyer layer  52  shown in circular dashed lines to indicate areas of adhesion inside the region bounded by circular dashed lines. The flyer layer  52  adheres to the substrate  54  in first adhesion regions  81 . The flyer layer adheres to the bridge  50  in a second adhesion region  82 . The flyer layer  52  adheres to the lands  42 ,  44  in third adhesion regions  83 . The flyer layer  52  adheres to the bridge portion  50  in the adhesion region  82 . 
         [0011]    In use, the lands  42 ,  44  are connected to a suitable current source (not shown). When sufficient current, for example, several hundreds of amps, is applied through the lands  42 ,  44 , the bridge member  50  vaporizes and is turned into a plasma. This plasma accelerates a portion of flyer layer  52  (“the flying plate”) away from the substrate  54  and towards an explosive (not shown). The shock of the flyer layer  52  striking the explosive detonates the explosive. 
         [0012]    In general, the dielectric material forming the flyer layer  52  adheres well to the ceramic substrate  54  in the first adhesion regions  81 , and to the bridge  50  formed from the buffer material  68  ( FIG. 3 ) in the second adhesion region  82 . However, since the lands  42 ,  44  are generally formed of a material selected for solder-ability, the dielectric material forming the flyer layer  52  may not adhere consistently to the lands  42 ,  44  in the third region  83 , leading to variability of performance of the chip slapper  46 . Furthermore, in chip slappers  46  where the exposed bridge portion  50  is formed of a conductor material, for example, if the buffer material  68  is omitted or if the second conductive layer  70  is not removed from the bridge  50 , the dielectric material forming the flyer layer  52  may not adhere consistently to the bridge  50  in the second region  82 . Therefore, there is a need in the industry to overcome the abovementioned shortcomings. 
       SUMMARY OF THE INVENTION 
       [0013]    Embodiments of the present invention provide devices and methods for a chip slapper with improved flyer layer adhesion. Briefly described, the present invention is directed to a chip slapper having a substrate, a conductive layer disposed above the substrate face, and an intermediate layer disposed between the substrate face and the conductive layer. The conductive layer and intermediate layer form a first land and a second land atop the substrate face, with a bridge formed of the intermediate layer spanning between the first land and the second land. A first adhesion portion is attached to the first land, and a second adhesion portion is attached to the second land, wherein at least a portion of the bridge is not overlaid by the first adhesion portion or the second adhesion portion. 
         [0014]    Other systems, methods and features of the present invention will be or become apparent to one having ordinary skill in the art upon examining the following drawings and detailed description. It is intended that all such additional systems, methods, and features be included in this description, be within the scope of the present invention and protected by the accompanying claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principals of the invention. 
           [0016]      FIG. 1  is a schematic view of a multi-layer wafer used to manufacture a number of prior art chip slappers. 
           [0017]      FIG. 2  is a schematic view of a portion of the prior art wafer shown in  FIG. 1  after the metal layers are etched to form the conductive lands and the bridge portion of an individual prior art chip slapper. 
           [0018]      FIG. 3  is schematic view of a portion of the prior art wafer shown in  FIG. 2  with the gold coating removed from the bridge portion of the prior art chip slapper. 
           [0019]      FIG. 4A  is a top view similar to  FIG. 3  with the flyer layer removed for clarity. 
           [0020]      FIG. 4B  is a top view similar to  FIG. 4A  with the flyer layer location shown in dashed lines. 
           [0021]      FIG. 5  is a schematic diagram of a top view of an exemplary first embodiment of a chip slapper detonator. 
           [0022]      FIG. 6  is a schematic diagram of a top view of an exemplary second embodiment of a chip slapper detonator. 
           [0023]      FIG. 7  is a flowchart of a method for forming a chip slapper detonator. 
           [0024]      FIG. 8  is a schematic diagram of a top view of an exemplary third embodiment of a chip slapper detonator. 
           [0025]      FIG. 9  is a schematic diagram of a top view of an exemplary fourth embodiment of a chip slapper detonator. 
           [0026]      FIG. 10  is a schematic diagram of a top view of an alternative embodiment of a chip slapper detonator. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    The following definitions are useful for interpreting terms applied to features of the embodiments disclosed herein, and are meant only to define elements within the disclosure. 
         [0028]    As used within this disclosure, an “exposed” area refers to a region of substrate or a layer of material layered above the substrate where a subsequent adjacent layer (or a portion thereof) has been removed, for example, by etching. 
         [0029]    As used within this disclosure “substantially” means, very nearly, or within typical manufacturing tolerances as would be appreciated by a person having ordinary skill in the art. For example, “substantially contiguous” indicates continuity between two elements despite insignificant gaps that do not generally affect the function of the elements. 
         [0030]    Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. 
         [0031]      FIG. 5  is a schematic diagram of a top view of an exemplary first embodiment of a chip slapper  200 . The first embodiment may be initially formed from the wafer  60  of  FIG. 1 , having a ceramic substrate layer  62 , a sticking layer  64 , for example, titanium tungsten, a conductive layer  66 , for example, copper, a buffer layer  68 , and a second conductive layer  70 , for example, a gold coating. The buffer layer  68  may be, for example, a titanium-tungsten or nickel composition. While the wafer  60  is shown for illustrative purpose for the first embodiment, wafers having different compositions are also possible. For example, the buffer layer  68  or other layers of the wafer  60  may be omitted, and other layers not shown in  FIG. 60  may be included, for example, additional buffer layers and/or sticking layers. 
         [0032]    As shown in  FIG. 5 , a first land  42 , a second land  44  and a bridge  50  spanning the first land  42  and the second land  44  may be formed by removing the layers above the substrate  54 , for example, by etching, exposing the substrate  54 . The first land  42 , the second land  44 , and bridge  50  are positioned between and separate two exposed surface regions of the substrate  54 . The first land  42 , the second land  44 , and the bridge  50  therefore each include a first edge (dash-dot line) defining a first boundary from a first exposed portion the substrate  54  and a second edge (dash-dot dot line) defining a second boundary from a second exposed portion of the substrate  54 . 
         [0033]    Unlike the prior art ( FIGS. 1-4 ), an adhesion layer  290  (or “adhesion portion”) is applied over the first land  42 , the second land  44 , the bridge  50 , and the substrate  54 . Under the first embodiment, the adhesion layer  290  may be formed in a ring shape, having an inner edge  292  with a first radius and an outer edge  291  with a second radius, where the second radius is larger than the first radius. The adhesion layer  290  may overlay an interface edge  251  between the material forming the surface of the first land  42  a, for example, gold, and the material forming the surface of the bridge  50 , for example, copper or a titanium-tungsten composition and also overlay an interface edge  251  between the material forming the second land  44 , for example, gold, and the material forming the surface of the bridge  50 , for example, copper or a titanium-tungsten composition. 
         [0034]    In general, the adhesion layer  290  preferably does not cover most or all of the bridge  50 . In particular, it is desirable, that the adhesion layer  290  is absent over portions of the bridge  50  where the flyer layer  52  is intended to separate upon detonation. In alternative embodiments, the adhesion layer  290  may not overlay any portion of the bridge  50 . 
         [0035]    The adhesion layer  290  is generally formed of a material conducive for adhesion to a dielectric coating such as polyimide or a Kapton® layer. For example, the adhesion layer  290  may be formed of a metal oxide of titanium, tungsten, titanium-tungsten, or chromium. Other metal oxides with good adhesive characteristics may also be used. Typically, gold is an undesirable material for the adhesion layer  290 , in part since gold does not make a good oxide. When formed as a ring shape, or otherwise when the portion of the adhesion layer  290  above the first land  42  is contiguous with the portion of the adhesion layer  290  above the second land  44 , as per the first embodiment, the adhesion layer  290  is preferably formed of a material that is not electrically conducting such as, but not limited to, silicon oxides. 
         [0036]    A flyer layer  252  overlays the adhesion layer  290 , as well as the entirety of the bridge  50 . The flyer layer  252  may also overlay a portion of the exposed portions of the substrate  54 , as well as a portion of the first land  42  and the second land  44 . For example, an outside radius of the flyer layer  252  is generally larger than the radius of the inner edge  292  of the adhesion layer  290 , and the outside radius of the flyer layer  252  may be less than, equal to, or larger than the larger radius of the outer edge  291  of the adhesion layer  290 . In a preferred embodiment, the outside radius of the flyer layer  252  may be slightly smaller than the radius of the outer edge  291 , for example, in the range of 1 to 1000 microns smaller. 
         [0037]    In general, a significant portion of the first land  42  and the second land  44 , are left exposed, and not covered by the flyer layer  252 , for example, half or more of the first land  42  and half or more of the second land  44 . The exposed portions of the first land  42  and/or the second land  44  may be used as electrical connection points or pads, for example, for soldering leads or other electrical components. The flyer layer  252  may include a dielectric coating such as polyimide or Kapton®. 
         [0038]    Preferably, the shape of the adhesion layer  290  conforms to the shape of all or a portion of the flyer layer  252 , which is applied over the adhesion layer  290 . Under the first embodiment, the flyer layer  52  is circular, and the adhesion layer  290  is ring shaped, conforming to the shape of the flyer layer  252 . However, the flyer layer  252  need not be circular. For example, in alternative embodiments, the flyer layer  252  may be rectangular. Further, the flyer layer  252  may be irregularly shaped, for example, having a rectangular profile for a portion covering the first land  42 , and a circular profile for a portion covering the second land  44 , among other possible configurations. A conforming shape of the adhesion layer  290  to the shape of the flyer layer  252  may facilitate cleaner separation of some or all of the flyer layer  252 . 
         [0039]      FIG. 6  is a schematic diagram of a top view of an exemplary second embodiment of a chip slapper  600 . Like the first embodiment, the second embodiment may be initially formed from the wafer  60  of  FIG. 1 , having a ceramic substrate layer  62 , a sticking layer  64 , a conductive layer  66 , a buffer layer  68 , and a second conductive layer  70 , for example, a gold coating. While the wafer  60  ( FIG. 1 ) is shown for illustrative purpose for the second embodiment, wafers having different compositions are also possible. For example, the buffer layer  68  or other layers of the wafer  60  may be omitted, and other layers not shown in  FIG. 6  may be included, for example, additional buffer layers and/or sticking layers. As shown in  FIG. 5 , a first land  42 , a second land  44 , and a bridge  50  spanning the first land  42  and the second land  44  may be formed by removing the layers above the substrate  54 , for example, by etching, exposing the substrate  54 . The first land  42 , the second land  44 , and the bridge  50  are positioned between and separate two exposed surface regions of substrate  54 . 
         [0040]    Unlike the first embodiment, where an adhesion layer  290  is applied over the first land  42 , the second land  44 , the bridge  50 , and the substrate  54 , under the second embodiment a first adhesion portion  691  is applied over the first land  42 , and a second adhesion portion  692  is applied over the second land  44 . 
         [0041]    Under the second embodiment, the first adhesion portion  691  and the second adhesion portion may be formed as arc shaped portions. The adhesion portions  691 ,  692  may overlay an interface edge  251  between the material forming the surface of the first land  42  and the second land  44 , for example, gold, and the material forming the surface of the bridge  50 , for example, copper or a titanium-tungsten composition, and also overlay an interface edge  251  between the material forming the second  44 , for example, gold, and the material forming the surface of the bridge  50 , for example, copper or a titanium-tungsten composition. 
         [0042]    In addition, the adhesion portions  691 ,  692  may extend to overlay a portion of the substrate  54 . However, in alternative embodiments the adhesion portions  691 ,  692  may not extend past the interface between the bridge  50  and the first land  42  and the second land  44  over the substrate  54 . In a third exemplary embodiment  800  shown by  FIG. 8 , the adhesion portions  891 ,  892  may overlay the material forming the surface of the bridge  50 , and not overlay the material forming the surface of the first land  42  and the second land  44 . In a fourth exemplary embodiment  900  shown in  FIG. 9 , adhesion portions  991 ,  992  may overlay only the material forming the surface of the first land  42  and the second land  44 , for example gold, and not overlay the material forming the surface of the bridge  50 . 
         [0043]    Returning to  FIG. 6 , in general, the adhesion portions  691 ,  692  preferably do not cover most or all of the bridge  50 . In particular, it is desirable, that adhesion portions  691 ,  692  are absent over portions of the bridge  50  where all or a portion of the flyer layer  52  is intended to separate from the chip slapper  600  upon activation. 
         [0044]    The adhesion portions  691 ,  692 ,  891 ,  892 ,  991 ,  992  are generally formed of a material conducive for adhesion to a dielectric layer, for example, polyimide or Kapton®. For example, the adhesion portions  691 ,  692 ,  891 ,  892 ,  991 ,  992  may be formed of a metal oxide of titanium, tungsten, titanium-tungsten, or chromium. Other metal oxides with good adhesive characteristics may also be used. Typically, gold is an undesirable material for the adhesion portions  691 ,  692 ,  891 ,  892 ,  991 ,  992 , for example, in part since gold does not make a good oxide. Since the adhesion portions  691 ,  692 ,  891 ,  892 ,  991 ,  992  are not contiguous, in contrast with the first embodiment described above, the adhesion portions  691 ,  692 ,  891 ,  892 ,  991 ,  992  may be formed of a material that is electrically conducting. 
         [0045]    A flyer layer  252  overlays the adhesion portions  691 ,  692 ,  891 ,  892 ,  991 ,  992 , as well as the entirety of the bridge  50 . The flyer layer  252  may also overlay an exposed portion of the substrate  54 , as well as a portion of the first land  42  and the second land  44 . As with the first embodiment, in general, a significant portion of the first land  42  and the second land  44 , are left exposed, and not covered by the flyer layer  252 , for example, half or more of the first land  42  and the second land  44 . The exposed portions of the first land  42  and the second land  44  may be used as electrical connection points or pads, for example, for soldering leads or other electrical components. The flyer layer  252  may be a dielectric coating such as polyimide or Kapton®. Preferably, the shape of the adhesion portions  691 ,  692 ,  891 ,  892 ,  991 ,  992  conforms to the shape of the flyer layer  252 , which is applied over the adhesion portions  691 ,  692 ,  891 ,  892 ,  991 ,  992 . 
         [0046]    Under the first, second, third and fourth embodiments, the adhesion of the dielectric material of the flyer layer  252  to the substrate  54  is improved over the prior art ( FIGS. 1-4 ) without significantly changing, compared to prior art described in the Background section, the mechanical/thermal/electrical or other characteristics of the flyer layer  252  in the critical central area of the bridge  50  where the flyer layer  252  is heated by an electrical current. 
         [0047]    The chip slapper  200  of the first embodiment, the chip slapper  600  of the second embodiment, the chip slapper  800  of the third embodiment, and the chip slapper  900  of the fourth embodiment may be incorporated into other detonator or explosive devices. For example, by adding additional layers over the chip slapper  200  of the first embodiment, the chip slapper  600  of the second embodiment, the chip slapper  800  of the third embodiment, and the chip slapper  900  of the fourth embodiment. 
         [0048]      FIG. 7  is a flowchart  700  showing an exemplary method for forming a chip slapper for a detonator device. It should be noted that any process descriptions or blocks in flowcharts should be understood as representing modules, segments, portions of code, or steps that include one or more instructions for implementing specific logical functions in the process, and alternative implementations are included within the scope of the present invention in which functions may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those reasonably skilled in the art of the present invention. 
         [0049]    An intermediate layer is applied over an exposed surface portion of a substrate  54  ( FIG. 6 ), as shown by block  710 . The intermediate layer may be, for example, a conductive layer or a buffer layer  68  ( FIG. 3 ), or a composite of a buffer layer and a conductive layer. The substrate  54  may be, for example, a ceramic substrate. A conductive layer  70  ( FIG. 3 ), is applied above the intermediate layer, as shown by block  720 . For example, the conductive layer may be a gold coating layer, or another electrically conductive material that provides a surface conducive to soldering. The intermediate layer and the conductive layer are removed from of a first region and a second region of the substrate  54  ( FIG. 6 ), for example by etching, leaving a first land  42  ( FIG. 6 ), a second land  44  ( FIG. 6 ), between the first region and the second region, as well as a bridge  50  ( FIG. 6 ) disposed between the first land  42  ( FIG. 6 ) and the second land  44 , as shown by block  730 . 
         [0050]    The conductive layer is removed from the bridge ( FIG. 6 ), as shown by block  740 , for example, by etching. A first adhesion portion  691  ( FIG. 6 ) is attached to the first land  42  ( FIG. 6 ), as shown by block  750 . A second adhesion portion  692  ( FIG. 6 ) is attached to the second land, as shown by block  760 . The first adhesion portion  691  ( FIG. 6 ) and the second adhesion portion  692  ( FIG. 6 ) may be attached, for example, by applying a layer of adhesive material over the underlying materials, and then etching the adhesive material to form a ring or two annular arcs. Alternatively, the first adhesion portion  691  ( FIG. 6 ) and the second adhesion portion  692  ( FIG. 6 ) may be applied with a lift-off procedure, or the first adhesion portion  691  ( FIG. 6 ) and the second adhesion portion  692  ( FIG. 6 ) may be deposited using a mask. The first adhesion portion  691  ( FIG. 6 ) and the second adhesion portion  692  ( FIG. 6 ) may also be attached by other means familiar to persons having ordinary skill in the art. A flyer layer  252  ( FIG. 6 ) is attached to the first adhesion portion  691  ( FIG. 6 ) and the second adhesion portion  692  ( FIG. 6 ), as shown by block  770 . In general, the first adhesion portion  691  ( FIG. 6 ) and the second adhesion portion  692  ( FIG. 6 ) serve to avoid variation of performance among chip slapper devices. 
         [0051]    It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. For example,  FIG. 10  shows an alternative embodiment  1000  based on the first embodiment shown in  FIG. 5 , where the adhesion layer  290  may be formed in a circle shape, rather than a ring shape. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.