Patent Publication Number: US-2007105412-A1

Title: Electrical Connector For A Window Pane Of A Vehicle

Description:
RELATED APPLICATIONS  
      This patent application is a continuation-in-part of and claims priority to and all advantages of U.S. patent application Ser. No. 10/988,350 which was filed on Nov. 12, 2004. 
    
    
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The subject invention generally relates to a window pane of a vehicle that includes an electrical connector and an electrical conductor. More specifically, the subject invention relates to an electrical connector that transfers electrical energy to an electrical conductor of the window pane, such as a defogger, defroster, antenna, etc.  
      2. Description of the Related Art  
      Electrical connectors are known in the art for use in vehicles. The connectors are soldered to and in electrical communication with an electrical conductor for transferring electrical energy to the conductor. More specifically, the conductors, which generally include sintered silver, are bonded to a substrate that is formed from glass, such as a backlite, sidelite, or windshield of a vehicle. The conductors are commonly visible on window panes of vehicles and typically extend horizontally across the window panes. The conductors are generally defoggers, defrosters, and antennas.  
      Traditionally, the connectors are soldered to the electrical conductors with a lead-based solder because lead is a deformable metal and minimizes mechanical stress between the connector and the substrate due to difference of thermal expansion of the connector and the substrate resulting from changes in temperature. More specifically, differences in coefficients of thermal expansion between the connectors, which are typically made of a good conductive material such as copper, and the substrates cause the mechanical stress. Such stress may result in cracking or other damage to the substrate, which is typically made of glass. Furthermore, the lead decreases the radical reaction rate between the tin in the solder and the silver in the conductor, allowing for good solderability. However, it is known that lead may be considered an environmental contaminant. As such, there is a motivation in many industries, including the automotive industry, to move away from all uses of lead in vehicles.  
      Conventional solder materials have been proposed that replace the lead in the solder with additional tin, along with small amounts of silver, copper, indium and bismuth. However, such materials have increased radical reaction rates between the tin-rich solder and the silver conductor, resulting in poor solderability. These conventional materials do not absorb the mechanical stress between the connector and the substrate due to thermal expansion of the connector and the substrate resulting from changes in temperature, which tends to crack or otherwise damage the substrate. Further, many alternative materials for the connector are difficult to solder, making it difficult to sufficiently adhere the connector to the conductor on the substrate. As a result, other techniques would be required in order to sufficiently adhere the alternative materials to the conductor on the substrate.  
      Although there has been development of various conductors for use in the window panes of vehicles, such developments have little applicability to electrical connector technology. For example, U.S. Pat. No. 6,396,026 discloses a laminated pane for a vehicle including an electrical conductor disposed between two glass panes. The electrical conductor includes a layered structure that may include titanium to provide rigidity to the electrical conductor. The electrical conductor is positioned in an interlayer between the panes. In this position, the electrical conductor is spaced from the glass panes. The titanium-containing conductor in the &#39;026 patent cannot effectively function as a connector that connects a power supply to a conductor that is bonded to one of the glass panes. More specifically, the titanium is disclosed as a core of the conductor, with an outer surface including a more conductive metal such as copper. The titanium core with the outer surface including copper is ineffective for use as an electrical connector due to the presence of the copper because the copper would delaminate from the conductor and/or cause the glass to crack due to mechanical stress between the copper and the glass pane due to thermal expansion of the copper and the glass pane resulting from changes in temperature.  
      Further, United States Patent Publication No. 2006/0056003 to Tonar et al. provides an electrical device that is typically used on a glass substrate. The electrical device includes a bus connection, i.e., an electrical connector, for supplying electrical power to an electro-optical element. The electrical connector is made from copper alloy or tin-plated copper, both of which are conventional materials that exhibit differences in coefficient of thermal expansion (with glass panes) that are too high. Although Tonar et al. provides that the electrical connector may utilize a metallic clip or strip that may be protected from the environment with metal plating or cladding, the metal plating or cladding performs no role in establishing a bond between the electrical connector and the glass substrate. Even more, many of the materials used for the metal plating or cladding are not of a type that would promote the establishment of a bond between the electrical connector and the connection site, and the difference in coefficients of thermal expansion between the electrical connector and the substrate eliminates any possibility of establishing the bond with a layer of solder.  
      U.S. Pat. No. 2,644,066 to Glynn provides an electric heater, i.e., an electric conductor, that is disposed on a glass substrate. A metal disc, i.e., an electrical connector, made from a low expansion material is soldered onto the electric heater for supplying electrical power to the electric heater. In terminal areas of the electric heater, a coating of solderable metal is sprayed onto the electric heater because the electric heater is formed from a thin layer of aluminum that is difficult to solder due to its strong surface oxide layer. The electrical connector is connected to the layer of solderable metal through a layer of solder. However, the electrical connector of Glynn is in direct contact with the solder, which is undesirable, especially when the connector is made from materials that are difficult to solder. Further, the solder used in Glynn includes lead, and Glynn does not account for the difficulties that are encountered with traditional solders that do not include lead.  
      Thus, there remains a need to provide connectors that may be bonded to the conductor through a layer of solder, that may be soldered with solders that do not include lead, that can still reduce the mechanical stress between the connector and the substrate due to thermal expansion of the connector and the substrate resulting from changes in temperature, and that reduce the radical reaction rate to allow for good solderability.  
     SUMMARY OF THE INVENTION AND ADVANTAGES  
      The subject invention provides a window pane. The window pane includes a substrate. The subject invention also provides an electrical device for a window pane, and a vehicle including the window pane. The window pane includes an electrical conductor and an electrical connector. A layer of solderable metal is bonded to the electrical connector. A layer of solder is bonded to the layer of solderable metal and the conductor, with the connector and the conductor in electrical communication through the layer of solderable metal and the layer of solder.  
      The substrate has a first coefficient of thermal expansion and the connector has a second coefficient of thermal expansion. A difference between the first and second coefficients of thermal expansion is equal to or less than 5×10 −6 /° C. for minimizing mechanical stress between the connector and the substrate due to thermal expansion of the connector and the substrate resulting from changes in temperature. As a result, the connector resists delamination from the substrate.  
      The layer of solderable metal bonded to the connector provides a site to bond to the layer of solder. More specifically, due to the difference between the first and second coefficients of thermal expansion, the connector is typically formed from a material that is difficult to solder, and the layer of solderable metal eliminates any difficulty in bonding the connector to the conductor.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:  
       FIG. 1  is a perspective view of a vehicle including a rear window pane having an electrical device;  
       FIG. 2  is a view of the window pane of  FIG. 1  with a power supply schematically illustrated;  
       FIG. 2   a  is a partial view a portion of the window pane of  FIG. 2  including an electrical connector bonded to an electrical conductor;  
       FIG. 3  is a schematic cross-sectional side view of the window pane taken along line  3 - 3  in  FIG. 2   a  illustrating the electrical conductor bonded to a ceramic layer, which is bonded to a substrate;  
       FIG. 4  is a schematic cross-sectional side view of another embodiment of the window pane illustrating the electrical conductor bonded to the substrate absent the ceramic layer;  
       FIG. 5  is a partial cross-sectional perspective view of yet another embodiment of the window pane including a cladding clad to the electrical connector; and  
       FIG. 6  is a schematic cross-sectional side view of the window pane taken along line  6 - 6  of  FIG. 5 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      Referring to the Figures, wherein like numerals indicate like or corresponding parts throughout the several views, a window pane is generally shown at  10  on a vehicle  12  in  FIG. 1 . The window pane  10  includes a substrate  14  that has a first coefficient of thermal expansion. The present invention also provides an electrical device  24  for a window pane  10  having a substrate  14 , with the electrical device  24  disposed on the substrate  14 . Further, the present invention provides the vehicle  12  including the window pane  10 .  
      Preferably, the substrate  14  is formed from glass; however, the substrate  14  may be formed from other materials such as ceramic. More preferably, the glass is further defined as an automotive glass. In a most preferred embodiment, the automotive glass is further defined as soda-lime-silica glass, which is well known for use in window panes  10  of vehicles  12 . However, it is to be appreciated that the glass may be any type of glass composition that is known in the art.  
      An electrical conductor  16  is applied across a region of the substrate  14 . Preferably, the conductor  16  includes silver; however, it is to be appreciated that other conductive metals may also be suitable for the conductor  16 . The electrical conductor  16  is visible on the pane  10  and typically includes lines  18  that extend horizontally across the pane  10 . The conductor  16  is preferably a defogger, defroster, antenna, or a combination thereof. However, the conductor  16  may serve any function known in the art for such conductors  16 .  
      Referring to  FIGS. 2 and 2   a , the window pane  10  further includes an electrical connector  20 . As shown in  FIG. 3 , a layer of solderable metal  32  is bonded to the connector  20 . A layer of solder  34  is bonded to the layer of solderable metal  32  and the conductor  16  with the connector  20  and the conductor  16  in electrical communication through the layer of solderable metal  32  and the layer of solder  34 . Together, the conductor  16 , the layer of solder  34 , the layer of solderable metal  32 , and the connector  20  form the electrical device  24 .  
      The electrical connector  20  has a second coefficient of thermal expansion. The connector  20  includes a metal having a low coefficient of thermal expansion (CTE). By “low coefficient of thermal expansion” it is meant that the metal has a sufficiently low CTE to make the difference between the first coefficient of thermal expansion of the substrate  14  and the second coefficient of thermal expansion of the connector  20  less than or equal to 5×10 −6 /° C., more typically less than or equal to 4×10 −6 /° C., most typically less than or equal to 3×10 −6 /° C.. Preferably, the connector  20  includes titanium; however other metals including, but not limited to, iron, molybdenum, tungsten, hafnium, tantalum, chromium, iridium, niobium, vanadium, platinum, and combinations thereof, as well as low CTE iron-nickel alloys, may be suitable for the connector  20  so long as a difference between the first coefficient of thermal expansion of the substrate  14  and the second coefficient of thermal expansion of the connector  20  is less than or equal to 5×10 −6 /° C., which will be described in further detail below. The titanium enables the connector  20  to reduce mechanical stress between the connector  20  and the substrate  14  due to thermal expansion of the connector  20  and the substrate  14  resulting from changes in temperature. More specifically, the mechanical stress is caused by differences between the first and second coefficients of expansion. The mechanical stress may cause cracking or other damage to the substrate  14 , and may also cause the connector  20  to separate from the substrate  14 .  
      Preferably, the titanium is present in the connector  20  in an amount of at least 50 parts by weight based on 100 parts by weight of the connector  20 . In a more preferred embodiment, the titanium is present in the connector  20  in an amount of at least 85 parts by weight, most preferably 99 parts by weight, based on 100 parts by weight of the connector  20 . A composition comprising 99 parts by weight of titanium based on 100 parts by weight of the composition is considered commercially pure titanium. In the most preferred embodiment, a remainder of the connector  20  may include iron, oxygen, carbon, nitrogen, and/or hydrogen, each of which may be present in an amount of less than or equal to 0.2 parts by weight based on 100 parts by weight of the connector  20 . Other residual elements may also be present in the connector  20  in an amount of less than 0.4 parts by weight based on 100 parts by weight of the connector  20 .  
      In another embodiment, the titanium may be an alloyed titanium that is alloyed with a metal selected from the group of aluminum, tin, copper, molybdenum, cobalt, nickel, zirconium, vanadium, chromium, niobium, tantalum, palladium, ruthenium, and combinations thereof. In this other embodiment, the metal is preferably present in the connector  20  in a total amount of from 0.05 to 50 parts by weight, more preferably from 1 to 10 parts by weight, most preferably from 1 to 5 parts by weight, based on 100 parts by weight of the connector  20 .  
      The titanium, as well as the solder composition that is typically free of lead (to be described in further detail below), is environmentally-friendly, and minimizes harmful effects to the environment to a greater extent than many other materials that are commonly used in connectors and solder compositions. Thus, waste tracking and disposal of excess titanium and solder composition from the manufacturing process and the processing of broken panes  10  is less stringent than for more environmentally harmful materials.  
      Besides environmental considerations, another advantage of the presence of titanium in the connector  20  is that the titanium has a substantially similar coefficient of thermal expansion to the substrate  14 , as briefly discussed above. Referring to  FIG. 4 , although the connector  20  and the substrate  14  are not directly connected, i.e., the conductor  16 , the layer of solderable metal  32 , and the layer of solder  34  are disposed between the substrate  14  and the connector  20 , the substrate  14 , which has the first coefficient of thermal expansion, is rigid and prone to cracking when subjected to mechanical stress resulting from expansion and contraction of the connector  20  due to changes in temperature. Preferably, the conductor  16  has a relatively small thickness from 4×10 −6  to 20×10 −6  m, as compared to the connector  20 , which typically has a thickness from 0.2×10 −3  to 2×10 −3  m. As a result of the small thickness and silver content of the conductor  16 , the conductor  16  is malleable or deformable and deforms when subjected to mechanical stress resulting from expansion and contraction due to changes in temperature. Thus, the conductor  16  absorbs much of the mechanical stress due to changes in temperature. However, the connector  20  also expands and contracts due to the changes in temperature, which also results in mechanical stress that is absorbed by the conductor  16 . As a result, substantial differences between the first and second coefficients of thermal expansion result in excessive mechanical stress on the conductor  16  and the substrate  14 . The substrate  14  is generally more brittle than both the connector  20  and the conductor  16  and cracks due to the mechanical stress.  
      As set forth above, a difference between the first and second coefficients of thermal expansion is equal to or less than 5×10 −6 /° C.., taken as an average over the temperature range of from 0 to 300° C., which is sufficient to avoid cracking of the substrate  14  up to and including a temperature of 600° C. Preferably, the first coefficient of thermal expansion is from 8 to 9×10 −6 /° C. As mentioned above, the substrate is preferably soda-lime-silica glass, which has a coefficient of thermal expansion of from 8.3 to 9×10 −6 /° C., most preferably about 8.3×10 −6 /° C., also taken as an average over a temperature range of from 0 to 300° C. Preferably, the second coefficient of thermal expansion is from 3 to 13×10 −6 /° C., most preferably about 8.8×10 −6 /° C., taken as an average over the temperature range of from 0 to 300° C.  
      As set forth above, the layer of solderable metal  32  is bonded to the connector  20 . More specifically, the bond between the layer of solderable metal  32  and the connector  20  is typically a mechanical bond and may be established by any known process including, but not limited to, cladding, sputtering, electroplating, or vacuum plating solderable metal onto the connector  20 .  
      The layer of solderable metal  32  may include any type of solderable metal that is capable of bonding to the connector  20  to establish the bond between the layer of solderable metal  32  and the connector  20 , and that further provides a binding site that exhibits excellent adhesion to the layer of solder  34 . Preferably, the solderable metal is capable of bonding to titanium. Typically, the solderable metal is selected from the group of copper, zinc, tin, silver, gold, and combinations thereof.  
      As set forth above, the layer of solder  34  is bonded to the layer of solderable metal  32  and the conductor  16 . Typically, the layer of solder  34  is bonded to the layer of solderable metal  32  and the conductor  16  by soldering.  
      The layer of solder  34  is formed from a solder composition. The solder composition typically includes tin and a reaction rate modifier, and is typically free of lead. The reaction rate modifier in the solder composition improves bonding between the conductor  16  and the layer of solderable metal  32 , as opposed to solder compositions that do not include the reaction rate modifier, and also serves the purpose of replacing at least a portion of the tin in the solder composition. Tin generates a compound with silver, such as the silver that may be in the conductor  16 , that helps form a strong bond between the layer of solder  34  and the conductor  16 . If solder does not include a certain amount of lead, this reaction is too radical and silver at the surface of the conductor  16  dissolves into the solder immediately, resulting in poor solderability and delamination between the layer of solder  34  and the conductor  16 . By including the reaction rate modifier in the solder composition instead of lead, the radical reaction may be suppressed and solderability improved in a way that is similar to when lead is included in the solder composition. The reaction rate modifier is typically a low-melting point metal, and may be selected from the group of, but is not limited to, bismuth, indium, zinc, and combinations thereof.  
      The reaction rate modifier is typically present in the solder composition in an amount of from 30 to 90 parts by weight based on 100 parts by weight of the solder composition. Most preferably, the reaction rate modifier is present in the solder composition in an amount of from 40 to 60 parts by weight, based on 100 parts by weight of the solder composition. The tin is typically included in the solder composition in an amount of from 10 to 70 parts by weight, most preferably from 25 to 50 parts by weight, based on 100 parts by weight of the solder composition. In addition to the tin and reaction rate modifier, the solder composition may also include other metals including, but not limited to, silver, copper, and combinations thereof for providing durability to the solder composition. When present, the silver may be included in an amount of equal to or less than 5 parts by weight based on 100 parts by weight of the solder composition. The copper may be included in an amount of equal to or less than 5 parts by weight based on 100 parts by weight of the solder composition, independent of the amount of silver included in the solder composition.  
      The layer of solderable metal  32  and the layer of solder  34  typically have a combined thickness that is sufficiently small to eliminate any effect of differences in coefficient of thermal expansion between the layer of solderable metal  32 , the layer of solder  34 , the connector  20 , and the substrate  14 . More specifically, the layer of solderable metal  32  and the layer of solder  34  typically have a combined thickness of less than or equal to 3.0×10 −4  m, based on experimental results, which is sufficiently small to make the coefficient of thermal expansion of both the layer of solderable metal  32  and the layer of solder  34  immaterial, especially when the connector  20  has a thickness as great as 2×10 −3  m. Due to the combined thickness of the layer of solderable metal  32  and the layer of solder  34  of less than or equal to 3.0×10 −4  m, and the position of the layer of solderable metal  32  and the layer of solder  34  between two relatively stiff materials, i.e., the connector  20  and the substrate  14 , the layer of solderable metal  32  and the layer of solder  34  will deform during heating and cooling instead of transmitting thermal expansion mismatch stress to the substrate  14 .  
      It is to be appreciated that the electrical device  24  of the present invention includes the connector  20 , the layer of solderable metal  32 , the layer of solder  34 , and the conductor  16 , to the exclusion of the substrate  14 . More specifically, the electrical device  24  exists separate from the substrate  14 , and the electrical device  24  need not necessarily be incorporated in conjunction with the window pane  10 .  
      Besides silver, the conductor  16  may also include other materials such as glass frit and flow modifiers. The conductor  16  is applied to the substrate  14  as a paste, which is subsequently fired onto the substrate  14  through a sintering process. More specifically, after the paste is applied to the substrate  14 , the substrate  14  is subjected to a low temperature bake at about 200° C., which causes the flow modifiers to flash out of the paste. The substrate  14  is then subjected to sintering at about 650° C., which fires the paste onto the substrate  14  to form the conductor  16 . The sintering process also prevents mechanical stress from developing between the conductor  16  and the substrate  14 .  
      When the conductor  16  is a defroster or defogger, the conductor  16  may further include vertical strips  50 ,  52 , in addition to the lines  18 , disposed on opposite ends of the lines  18 . The strips  50 ,  52  electrically connect the lines  18 . The strips  50 ,  52 , in combination with the lines  18 , form a parallel circuit.  
      Referring to  FIGS. 2 and 3 , the pane  10  may include a ceramic layer  26  disposed adjacent to a periphery of the pane  10 . The ceramic layer  26  protects an adhesive on the substrate  14  from UV degradation. As known in the art, such adhesive is typically utilized to adhere the pane  10  to a body of the vehicle  12 . Thus, as shown in  FIG. 3 , the ceramic layer  26  may be disposed between the substrate  14  and the conductor  16 . The ceramic layer  26  is generally black in color and has a negligible effect on the thermal expansion dynamics between the substrate  14 , the conductor  16 , and the connector  20 . Thus, in terms of thermal expansion dynamics, there is no significant difference between the configuration as shown in  FIG. 3 , wherein the connector  20  is bonded to the conductor  16  on top of the ceramic layer  26 , and the configuration as shown in  FIG. 4 , wherein the connector  20  is bonded to the conductor  16  on top of the substrate  14 .  
      In one embodiment, shown in  FIGS. 5 and 6 , the connector  20  has an outer surface area  28  and a cladding  30  clad to the outer surface area  28 . It is to be appreciated that “cladding” refers to a layer of metal bonded to a metal substrate, in this case the connector  20 , and is not in any way limited to a method by which the cladding  30  is formed on the connector  20 . Preferably, the cladding  30  includes a metal selected from the group of copper, silver, aluminum, gold, and combinations thereof. The cladding  30  is more electrically conductive than the titanium to improve flow of electricity through the connector  20 . The cladding  30  is spaced from the conductor  16  such that the cladding  30  is mechanically insulated from the conductor  16  to avoid undue mechanical stress on the substrate  14  as discussed above, since the cladding  30  has a substantially different coefficient of thermal expansion from the substrate  14 .  
      Preferably, the cladding  30  and the connector  20  are present relative to one another in a volumetric ratio of from 0.01:1 to 4:1 such that the connector  20  includes enough titanium to sufficiently minimize the mechanical stress caused by expansion and contraction of the cladding  30  due to the changes in temperature.  
      In another embodiment, the connector  20  may comprise the alloyed titanium that has 50 parts by weight or less of copper based on 100 parts by weight of the connector  20 , with the balance comprising titanium, to eliminate the need for the cladding  30 .  
      The connector  20  transfers electrical energy to the conductor  16 . Typically, the connector  20  is connected to the conductor  16 , through the layer of solderable metal  32  and the layer of solder  34 , adjacent the periphery of the pane  10  on one side of the pane  10 . Preferably, a second connector  22  is bonded to and in electrical communication with the conductor  16 , also through a layer of solderable metal  32  and a layer of solder  34 , on an opposite side of the pane  10  from the connector  20 . However, it is to be appreciated that the second connector  22  is optional. The second connector  22  may transfer electrical energy away from the conductor  16 . In one embodiment, as shown schematically in  FIG. 2 , the vehicle  12  includes the power supply  38  for providing the electrical energy. The power supply  38  may be a battery, alternator, etc. Preferably, both the connector  20  and the second connector  22  are operatively connected to and in electrical communication with the power supply  38 . The connector  20  transfers electrical energy from the power supply  38  to the conductor  16 , through the layer of solderable metal  32  and the layer of solder  34 , and the second connector  22  transfers electrical energy from the conductor  16  to the power supply  38 . More specifically, a lead wire  40  is operatively connected to and extends from the power supply  38  adjacent to the substrate  14 . The lead wire  40  is also operatively connected to the connector  20 . Another wire  42  extends from the power supply  38  to the second connector  22  and is operatively connected to the second connector  22  to complete an electrical circuit. The lead wire  40  and the wire  42  preferably include copper.  
      The operative connection between the lead wire  40  and the connector  20  may be formed through welding, a mechanical connection, etc. In one embodiment, a female member  46  extends from one of the connector  20  and the lead wire  40 . A male member  48  extends from the other of the connector  20  and the lead wire  40  for operatively connecting to the female member  46 . That is, as shown in  FIG. 5 , the female member  46  can extend from the lead wire  40  when the male member  48  extends from the connector  20 , and vice versa. The operative connection between the second connector  22  and the second lead wire  42  may be the same as the operative connection between the connector  20  and the lead wire  40 . In a most preferred embodiment, shown in  FIG. 5 , the lead wire  40  includes the female member  46  and the connector  20  includes the male member  48 . The female member  46  engages the male member  48  through compression to prevent separation between the lead wire  40  and the connector  20 . However, it is to be appreciated that the members  46 ,  48  may be connected through welding or other processes.  
     EXAMPLES  
      Test plaques were made including the glass substrate  14 , the electrical conductor  16 , the electrical connector  20  including the layer of solderable metal  32 , and the layer of solder  34 . Half of the test plaques include glass substrates  14  with a ceramic layer  26 , and the electrical conductor  16  was bonded to the glass substrate  14  over the ceramic layer  26 . However, the results were the same for both configurations. The electrical conductor  16  was formed from silver paste for all of the plaques, and the silver paste was fired onto the substrate  14  to form the electrical conductor  16 . The layer of solderable metal  32  was formed on the connector  20  by sputtering. The connector  20  was soldered to the conductor  16  through the layer of solder  34 . The electrical connector  20 , the layer of solderable metal  32 , and the layer of solder  34  were formed from metals as indicated in Table 1. The glass substrate  14  was formed from soda-lime-silica  
      Further, the connectors soldered to the plaques were subjected to a pull test at least 24 hours after soldering. Referring to Table 1, the type and amount of metal used for the connector  20 , the layer of solderable metal  32 , and the layer of solder  34  are shown for each of the plaques, with amounts in parts by weight based on 100 parts by weight of the connector  20 , the layer of solderable metal  32 , or the layer of solder  34 , respectively, along with an indication of whether or not the plaque exhibits sufficient performance when subjected to changes in temperature. Furthermore, the properties of the soda-lime-silica glass are also included in the Table 1.  
                           TABLE 1                           Material   Ex. A   Ex. B                                                Electrical   Titanium   100.00   100.00       Connector   Avg. CTE, ×10 −6 /° C. over range   8.80   8.80           of 0-100° C.           Difference between CTE of Connector   0.5   0.5           and Glass Substrate, ×10 −6 /° C.           over a range of 0-100° C.           Thickness of Electrical Connector, m   8.0 × 10 −4     8.0 × 10 −4         Layer of   Copper   100.00   100.00       Solderable   Thickness of Layer of Solderable   5.0 × 10 −6     5.0 × 10 −6         metal   Metal, m       Layer of solder   Tin   48   30           Bismuth   46   64           Silver   2   2           Copper   4   4           Thickness of Layer of Solder, m   50-200 × 10 −6     50-200 × 10 −6             Combined Thickness of Layer of   55-205 × 10 −6     55-205 × 10 −6             Solderable Metal and Layer of Solder, m       Glass Substrate   Avg CTE, ×10 −6 /° C. over   8.3   8.3       (Soda-Lime-   range of 0-302° C.       Silica)   Results of Pull Test   Good Pull   Good Pull               Strength   Strength                  
 
     COMPARATIVE EXAMPLES  
      Comparative Examples of plaques are made for comparison to the plaques made in accordance with the present invention. More specifically, plaques for Comparative Examples A thru D were made the same as set forth above in the Examples, except for the amount of reaction rate modifier used and the thickness of the layer of solderable metal. In Comparative Example B, no layer of solderable metal is present. Referring to Table 2, the type and amount of metal used for the connector and the layer of solder are shown for each of the plaques, with amounts in parts by weight based on 100 parts by weight of the connector or the layer of solder, respectively, along with an indication of whether or not the plaque exhibits sufficient performance when subjected to changes in temperature. Furthermore, the properties of the soda-lime-silica glass are also included in the Table 2.  
                           TABLE 2                              Material   Comp. Ex. A   Comp. Ex. B               Electrical   Titanium   100.00   100.00       Connector   Avg. CTE, ×10 −6 /° C. over range of 0-100° C.   8.80   8.80           Difference between CTE of Connector   0.5   0.5           and Glass Substrate, ×10 −6 /° C. over a           range of 0-100° C.           Thickness of Electrical Connector, m   8.0 × 10 −4     8.0 × 10 −4         Layer of           None       Solderable metal           Copper   100.00   0.00           Thickness of Layer of Solderable   500 × 10 −6     0.00           Metal, m       Layer of solder   Tin   48   48           Bismuth   46   46           Silver   2   2           Copper   4   4           Thickness of Layer of Solder, m    50-200 × 10 −6     50-200 × 10 −6             Combined Thickness of Layer of   550-700 × 10 −6     50-200 × 10 −6             solderable metal and Layer of solder, m       Glass Substrate   Avg CTE, ×10 −6 /° C. over range of 0-302° C.   8.3   8.3       (Soda-Lime-Silica)   Results of Elevated Temperature Test   Substrate   No               cracks,   adhesion               Poor pull               strength                   Material   Comp Ex. C   Comp Ex. D               Electrical   Titanium   100.00   100.00       Connector   Avg. CTE, ×10 −6 /° C. over range of 0-100° C.   8.80   8.80           Difference between CTE of Connector   0.5   0.5           and Glass Substrate, ×10 −6 /° C. over a           range of 0-100° C.           Thickness of Electrical Connector, m   8.0 × 10 −4     8.0 × 10 −4         Layer of   Copper   100.00   100.00       Solderable metal   Thickness of Layer of Solderable   5.0 × 10 −6     5.0 × 10 −6             Metal, m       Layer of solder   Tin   90   48           Bismuth   7.5   46           Silver   2.0   2           Copper   0.5   4           Thickness of Layer of Solder, m   50-200 × 10 −6     400-500 × 10 −6             Combined Thickness of Layer of   55-205 × 10 −6     405-505 × 10 −6             solderable metal and Layer of solder, m       Glass Substrate   Avg CTE, ×10 −6 /° C. over range of 0-302° C.   8.3   8.3       (Soda-Lime-Silica)   Results of Elevated Temperature Test   Poor   Substrate               solderability,   cracks,               Poor pull   Poor pull               strength   strength                  
 
      Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.