Patent Publication Number: US-2009236134-A1

Title: Low frequency ball grid array resonator

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
     This non-provisional application claims the benefit of U.S. Provisional Application Ser. No. 61/070,247 filed on Mar. 20, 2008, the disclosure of which is explicitly incorporated herein by reference as are all references cited therein. 
    
    
     BACKGROUND OF THE INVENTION  
     YIG (Yttrium-Iron-Garnet) oscillators, DROs (dielectric resonator oscillators), coaxial resonators, and cavity resonators of the type made and sold by, for example, Dielectric Laboratories Inc. of Cazenovia, N.Y., have been in use for the past several years for the purpose of providing precise frequency control references in products such as voltage controlled oscillators. 
     Although the above devices have gained acceptance in the marketplace, there remains a need for an RF resonator capable of offering selectivity and other performance improvements at 1.8 GHz or lower, all in a lower cost, smaller, higher performance, and lower height ball grid array type package. This invention provides such an improved ceramic ball grid array type resonator. 
     SUMMARY OF THE INVENTION  
     The resonator of the present invention is adapted for use as a shorted element or high “Q” inductive element in the tank circuit of, for example, a 900 MHz VCO (voltage controlled oscillator) or VCO/PLL (voltage controlled oscillator/phase locked loop). 
     In one embodiment, the present invention is directed to a ball grid array resonator which initially comprises a ceramic substrate which defines first and second outer opposed surfaces. The resonator further comprises an RF signal transmission line defined by the combination of a first elongate strip of conductive material which is formed on the first surface, a second elongate strip of material which is formed on the second surface, and a conductive via which extends through the substrate and interconnects the first and second strips of material. The resonator still further comprises at least a first conductive ball/sphere on the first surface which defines an RF signal input/output pad in electrical coupling relationship with the first strip of conductive material thereon and a second conductive ball/sphere on the first surface which defines a ground pad. 
     In accordance with one embodiment of the invention, at least one of the first or second strips of conductive material has a curving pattern such as, for example, a spiral pattern, a serpentine pattern, or a hook-shaped pattern. 
     Moreover, in accordance with one embodiment of the invention, the RF transmission line further comprises another conductive via which extends through the substrate and is in electrical contact with both the second elongate strip of conductive material and a third conductive ball/sphere on the first surface which defines another RF signal input/output pad. 
     The respective RF signal input/output balls/spheres and ground balls/spheres are adapted to be seated on and electrically connected to the respective RF signal input/output pads and ground pads on the printed circuit board of an oscillator such as, for example, the tank circuit portion of a voltage controlled oscillator. 
     Other advantages and features of the present invention will be more readily apparent from the following detailed description of the preferred embodiments of the invention, the accompanying drawings, and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
       These and other features of the invention can best be understood by the following description of the accompanying drawings as follows: 
         FIG. 1  is an enlarged, top perspective view of one embodiment of a low frequency ball grid array resonator in accordance with the present invention, without a lid; 
         FIG. 2  is an enlarged, bottom perspective view of the resonator of  FIG. 1 ; 
         FIG. 3  is an enlarged, top perspective view of another embodiment of a low frequency ball grid array resonator in accordance with the present invention, without a lid; 
         FIG. 4  is an enlarged, bottom perspective view of the resonator shown in  FIG. 3 ; 
         FIG. 5  is an enlarged, top perspective view of yet another embodiment of a low frequency ball grid array resonator in accordance with the present invention, without a lid; 
         FIG. 6  is an enlarged, bottom perspective view of the resonator of  FIG. 5 ; 
         FIG. 7  is an enlarged, top perspective view of a further embodiment of a low frequency ball grid array resonator in accordance with the present invention, without a lid; and 
         FIG. 8  is an enlarged, bottom perspective view of the resonator of  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION  
     While this invention is susceptible to embodiments in many different forms, this specification and the accompanying drawings disclose only four respective embodiments of low frequency ball grid array resonators of the present invention. The invention is not intended, however, to be limited to the four embodiments so described. 
       FIGS. 1 and 2  depict a ceramic ball grid array (BGA) microstrip resonator  20  according to the present invention which, in the embodiment shown, measures about 6.0 mm (length)×3.0 mm (width)×1.3 mm (height) (maximum). 
     Resonator  20  initially comprises a generally rectangularly-shaped substrate or block  22  comprised of any suitable dielectric material that has relatively low loss, a relatively high dielectric constant, and a relatively low temperature coefficient of the dielectric constant. In the embodiment of  FIGS. 1-2 , substrate  22  is about 20 mils (0.5 mm) thick and is comprised of a ceramic substrate which is about 96% aluminum oxide (Al 2 O 3 ). In the preferred embodiment, substrate  22  has a Q of between about 200-300 and a dielectric constant (K) of about 9.5. 
     Substrate  22  includes a top surface  24  ( FIG. 1 ), a bottom surface  26  ( FIG. 2 ), and respective side surfaces defining respective long side/longitudinal opposed peripheral edges  28  and  30  and opposed short side/transverse peripheral edges  32  and  34  respectively. 
     In the embodiment shown, resonator  20  defines at least a pair of generally cylindrically-shaped laser drilled through-holes defining conductive vias  36   a  and  36   b  ( FIGS. 1 and 2 ) which are approximately 8 mils (0.20 mm) in diameter and are formed in and extend generally vertically through the body of substrate  22  between, and in a relationship generally normal to, the top and bottom surfaces  24  and  26  respectively. Vias  36   a  and  36   b  terminate in, and define via termination apertures/ends in both the top and bottom surfaces  24  and  26  respectively of the substrate  22 . 
     In the embodiment of  FIGS. 1 and 2 , via  36   a  is preferably centrally located on substrate  22  while via  36   b  is located centrally adjacent the edge  32  of substrate  22  in a relationship generally co-linear with via  36   a.    
     Although not shown in any of the FIGURES, it is understood that the vias  36   a  and  36   b  are defined by respective through-holes which have been filled with a suitable and conventional thick film conductive via fill material, such as a Ag/Pd (silver/palladium) composition comprising about 99% silver and 1% palladium; having a conductivity of about 4.3×10 7  mho/cm; a resistivity of about 2.3 μohm-cm; and a sheet resistance of about 2.2 ohm/square. 
     A plurality of solder spheres or balls  50   a - 50   d  ( FIG. 2 ), each with a pitch of a minimum of about 1.0 mm and a diameter of about 0.025 inches (0.64 mm), are mechanically and electrically attached to the bottom surface  26  of substrate  22 . Spheres  50   a - 50   d  are composed of any suitable high temperature solderable material which does not reflow or change shape such as, for example, a 90% Pb and 10% Sn composition (or a lead-free copper with Sn/Ni plating composition if desired) and are adapted to allow the direct surface mounting of the resonator  20  to the printed circuit board of, for example, a GSM base station. Although not described in detail herein or shown in any of the drawings, it is understood that the spheres  50   a - 50   d  could also take the form of pads or strips of conductive material. 
     In the embodiment shown, substrate  22  includes four spheres  50   a ,  50   b ,  50   c , and  50   d  attached to the surface  26  of substrate  22  ( FIG. 1 ). Spheres  50   a ,  50   b , and  50   c  extend in a spaced-apart relationship along and adjacent the edge  32  of substrate  22 . Sphere  50   b  is attached to and overlies the end of via  36   b  which terminates in bottom substrate surface  26 . Sphere  50   d  is located generally centrally on the substrate  22  adjacent substrate edge  34  in a relationship generally co-linear with via  36   a  and diametrically opposed to sphere  50   b.    
     The solder spheres  50   a  and  50   c  define respective ground pins or pads adapted to be electrically connected to the respective ground pads of the external printed circuit board to which the resonator  20  is adapted to be direct surface mounted. 
     Solder spheres  50   b  and  50   d  define the RF signal input/output pins or tap pads of resonator  20  and are adapted for electrical coupling to the respective RF signal input/output pads of the external printed circuit board (not shown) to which the resonator  20  is adapted to be direct surface mounted. 
     The top and bottom surfaces  24  and  26  of resonator  20  additionally define respective conductive metallization resonator patterns  42  and  44  ( FIGS. 1 and 2 ), each defined by an elongate unitary strip of conductive material which has been formed on the top and bottom surfaces  24  and  26  of substrate  22  by any suitable technique including, but not limited to, conventional thick film conductor processing techniques or conventional ablation techniques. Each of the resonator strips is likewise comprised of a suitable and conventional Ag/Pd conductive thick film material similar in composition to the material in vias  36   a  and  36   b.    
     Elongate resonator strip  42  on top surface  24  defines a first end  42   a  coupled to and surrounding the termination end of via  36   b  defined in the top surface  24  of substrate  22 . Strip  42  additionally defines a generally straight segment  42   b  which extends generally centrally on top surface  24  downwardly away from via  36   b  in a relationship parallel to long side substrate peripheral edges  28  and  30 ; and a generally centrally located “3.5 turn” curved spiral segment  42   c  defining a spiral end  42   d  which is electrically coupled to and surrounds the termination end of via  36   a  protruding in surface  24 . 
     Elongate resonator strip  44 , which is oriented and positioned on bottom surface  26  in a relationship diametrically opposed to resonator strip  42  on top surface  24 , defines a first end  44   a  which is electrically coupled to and surrounds sphere  50   d ; a generally straight segment  44   b  which extends generally centrally on substrate surface  26  downwardly away from the sphere  50   d  and end  44   a  in a relationship parallel to long side substrate peripheral edges  28  and  30 ; and a generally centrally located “2.5 turn” curved spiral segment  44   c  defining a spiral end  44   d  which is electrically coupled to and surrounds the termination end of via  36   a  which protrudes into surface  26 . In the embodiment shown, spiral segment  44   c  of strip  44  has a smaller diameter than spiral segment  42   c  of strip  42 . 
     Thus, in accordance with the present invention, it is understood that an RF signal is adapted to be transferred and passed from the RF input pad (not shown) of a customer&#39;s printed circuit board (not shown) to either the sphere  50   d  or the sphere  50   b  of resonator  20  since either may comprise an RF signal input. In the application where the RF signal is inputted through the sphere  50   d  sifting atop strip end segment  44   a,  the RF signal flows successively from sphere  50   d , downwardly through strip segments  44   a,    44   b,  and  44   c  of strip  44 , then upwardly through the interior of substrate  22  through via  36   a , then successively through strip segments  42   c ,  42   b , and  42   a  of strip  42 , then back down through the interior of substrate  22  through via  36   b  into sphere  50   b , and finally into the RF signal output pad (not shown) of the printed circuit board or substrate of, for example, a voltage controlled oscillator module (not shown). 
     Thus, in accordance with the present invention, elongate resonator strips  42  and  44  in combination with the substrate vias  36   a  and  36   b  and the spheres  50   b  and  50   d  together define an elongate, continuous RF signal transmission line/pathway/strip/pattern extending through the resonator  20 . 
     The frequency of the RF signal passing through the resonator  20  is dependent in part upon the length and configuration of resonator strips  42  and  44 . The length, of course, can be increased or decreased, for example, by increasing or decreasing the number of turns in the respective curved spiral segments of each of the respective resonator strips  42  and  44  and/or increasing or decreasing the length of the respective straight segments  42   b  and  44   b  and/or increasing or decreasing the width of the respective strips  42  and  44 . 
     For example, it is understood that a shortening or decrease in the length of strips  42  and  44  will result in a corresponding increase in the effective frequency of resonator  20 , while an increase in the length of one or both of the strips  42  and  44  will result in a corresponding decrease in the effective frequency of the resonator  20 . This frequency is generally the quarter wavelength frequency of the resonator. The desired frequency and application for resonator  20  will, of course, determine the respective effective lengths of strips  42  and  44 . 
     Although not shown in any of the FIGURES, it is further understood that resonator  20  may additionally comprise an optional metal lid which may be about 20 mils (0.5 mm high), adapted to be seated over and secured to the top surface  24  of substrate  22  and provide several functions including: providing an air gap above the resonator strip pattern  42 ; functioning as a Faraday shield; defining a ground plane above resonator strip pattern  42 ; and acting as a dust cover for resonator  20 . 
     Resonator  20  is preferably assembled using the following process sequence: A substrate  22  is provided and the through-holes/vias are laser-drilled therethrough. Via fill material paste is then screened over each of the through-hole openings. Both of the surfaces  24  and  26  of the substrate  22  are then rolled to force the fill material through the through-holes to define the vias  36   a  and  36   b . Substrate  22  is then fired in an oven at approximately 850° C. to cure the via fill material. 
     Resonator conductive strip patterns  42  and  44  are then subsequently formed on the top and bottom surfaces  24  and  26  of substrate  22  as by, for example, a screening or plating process or an ablative process followed by firing in an oven at about 850° C. to cure the Ag/Pd conductive material. 
     A generally translucent optional protective coating or masking layer of dielectric material called a glasscoat may then be screen printed over the portion of the top and bottom surfaces  24  and  26  of the substrate  22  and the substrate  22  is again fired in an oven at about 850° C. to cure the coat layer of dielectric material.  FIG. 2  shows glasscoat layer  60 . This coating is not optional on the bottom surface  26 , as it defines the positions of the solder balls. 
     Solder paste is then screen printed over the top surface  22  in the region adjacent each of the side edges thereof and the optional lid (not shown) may be seated over the top surface  24  of substrate  22 . The solder is then reflowed to secure the optional lid to the substrate  22 . 
     Solder paste (not shown) is also screen printed on the bottom surface  26  of substrate  22  (see  FIG. 2 ) in the regions thereof where conductive spheres  50   a - 50   d  are adapted to be seated. All of the conductive spheres  50   a - 50   d  are then seated over each of the points of solder paste and the solder paste is subsequently reflowed for permanently securing the solder spheres  50   a - 50   d  to the substrate  22 . 
     Finally, resonator  20  is tested and then taped and reeled for shipment. 
       FIGS. 3 and 4  depict a second resonator embodiment  220  in accordance with the present invention. 
     Initially, and as described earlier with respect to the resonator embodiment  20 , resonator  220  likewise initially comprises a generally rectangularly-shaped substrate or block  222  which preferably has the same dimensions and composition as the substrate  22  and thus the earlier discussion and description with respect to substrate  22  is hereby incorporated herein by reference. 
     Substrate  222  includes a top surface  224  ( FIG. 3 ), a bottom surface  226  ( FIG. 4 ) adapted to face the top of the printed circuit board (not shown) on which the resonator  220  is adapted to be seated and direct surface mounted, and side surfaces defining long side/longitudinal peripheral edges  228  and  230  and short side/transverse peripheral edges  232  and  234  respectively. 
     Resonator  220  further includes a pair of elongate laser drilled through-holes defining conductive vias  236   a  and  236   b  which extend through the body/interior of the substrate  222  and terminate in respective apertures/openings in the top and bottom substrate surfaces  224  and  226 . Vias  236   a  and  236   b  extend through the substrate  222  in a generally normal relationship relative to the top and bottom substrate surfaces  224  and  226 . 
     In the embodiment of  FIGS. 3 and 4 , via  236   a  is generally centrally located and formed adjacent to and spaced from the short side substrate edge  232  while via  236   b  is generally centrally located and formed adjacent to and spaced from the long side substrate edge  228 . Vias  236   a  and  236   b  are filled with the same Ag/Pd material as described above with respect to vias  36   a  and  36   b  of resonator  20  and thus the earlier description is incorporated herein by reference. 
     In a manner similar to resonator embodiment  20 , resonator  200  likewise includes conductive solder spheres  250   a ,  250   b ,  250   c , and  250   d  (similar in size and composition to spheres  50   a - 50   d , the description of which is thus incorporated herein by reference) positioned and secured to the bottom surface  226  of substrate  222 . Specifically, spheres  250   a ,  250   b , and  250   c  are aligned and extend along and adjacent the short side substrate edge  232  in a generally co-linear, spaced-apart relationship with sphere  250   b  overlying via  236   b . Sphere  250   d  is generally centrally located along opposed short side substrate edge  234  in a relationship diametrically opposed to and co-linear with sphere  250   b.    
     Moreover, and as shown in  FIGS. 3 and 4 , each of the surfaces  224  and  226  of substrate  222  defines respective elongated conductive thick film resonator metallization pattern or strips  242  and  244  similar in composition to resonator metallization strips  42  and  44  of resonator  20 , the description of the composition of each of such strips thus being incorporated herein by reference as though fully described except as otherwise described below. 
     Resonator strip  242  is generally curved and, more specifically, hook-shaped and is defined by one proximal curvilinear end  242   a  which is electrically coupled to and surrounds the aperture/end of via  236   a  terminating in substrate surface  224 ; a generally straight segment  242   b  extending generally downwardly away from via  236   a  in a relationship and orientation generally parallel, spaced from, and adjacent to longitudinal long side substrate edge  230 ; a hook portion/segment  242   c  defining a curvilinearly-shaped base portion disposed generally adjacent and spaced from substrate short side edge  234  and extending in the direction of substrate long side edge  228 ; and a terminal straight portion/segment  242   d  which extends generally upwardly away from base portion  242   c  in the direction of substrate short side edge  232  in a relationship spaced from and generally parallel to long side substrate edge  228  and terminating in a distal end  242   e  which is electrically coupled to the end/aperture of via  236   b  terminating in substrate surface  224 . 
     Resonator strip  244  which has the same curved, hook-shaped configuration as resonator strip  242 , and is positioned and oriented on surface  226  in a relationship diametrically opposed to resonator strip  242  on surface  224 , is defined by one proximal end  244   a  which is electrically coupled to and surrounds the sphere  250   d ; a generally straight segment  244   b  extending generally downwardly away from sphere  250   d  in a relationship and orientation generally parallel, adjacent to, and spaced from long side substrate edge  230 ; a hook portion/segment  244   c  defining a curvilinearly-shaped base portion disposed generally adjacent and spaced from substrate short side edge  232  and spheres  250   a - 250   c  and extending in the direction of substrate long side edge  228 ; a terminal straight portion/segment  244   d  which extends generally upwardly away from base portion  244   c  in the direction of substrate short side edge  234  in a relationship spaced from, adjacent to, and generally parallel to long side substrate edge  228 ; and a terminal end  244   f  which is electrically coupled to and surrounds the end/aperture of via  236   b  terminating in bottom surface  226 .  FIG. 4  shows glasscoat layer  260 , similar to glasscoat layer  60  of resonator  20 , formed over strip  244  and surface  226  of resonator  220 . 
     Thus, in view of the above, and as explained above with resonator embodiment  20 , it is understood that the formation and use of elongate resonator strips  242  and  244  on opposed substrate surfaces  224  and  226  in coupling electrical relationship with respective vias  236   a  and  236   b  and spheres  250   b  and  250   d  defines a continuous elongate RF signal transmission line/pathway/strip/pattern extending through the resonator  220  which makes the resonator  220  particularly suited and adapted for low frequency applications, i.e., applications in the range below about 1.8 GHz. 
     Moreover, in the resonator embodiment  220  of  FIGS. 3 and 4 , respective resonator strips  242  and  244  have a width which is generally about one quarter the width of the resonator  220  or about twice the width of each of the resonator strips  42  and  44  of resonator embodiment  20 . It is understood, of course, that increasing the width of the resonator strips results in a resonator with increased or heightened “Q” value since resistance decreases in proportion to an increase in the width of a conductive element. 
     In accordance with this embodiment of the invention and referring to  FIGS. 3 and 4 , the RF signal is adapted to pass successively from the RF input pad on the PCB (not shown) into and through either the solder sphere  250   b  or  250   d  depending upon the application. Solder spheres  250   b  and  250   d  both define respective RF signal input/output pads. In the application where the RF signal is inputted through the sphere  250   d  sitting atop end strip portion  244   a  of resonator of resonator strip  244 , the RF signal passes from the sphere  250   d  and then through the resonator strip  244  in a generally clockwise direction through the length of resonator strip  244 ; then upwardly through the interior of substrate  222  through via  236   b ; then generally counter-clockwise through the length of resonator strip  242  on top surface  224 ; and then back down and through the interior of board substrate  222  through via  236   a  into sphere  250   b  and into the RF signal output pad (not shown) of a printed circuit board. 
       FIGS. 5-6  depict yet another low frequency resonator embodiment  320  in accordance with the present invention. 
     Initially, and as described earlier with respect to the resonator embodiments  20  and  220 , resonator  320  likewise initially comprises a generally rectangularly-shaped substrate or block  322  having the same dimensions and composition as the substrates  22  and  222  and thus the earlier discussion and description relating to substrates  22  and  222  is expressly hereby incorporated herein by reference. 
     Substrate  322  includes a top surface  324  ( FIG. 5 ), a bottom surface  326  ( FIG. 6 ) adapted to face the top of a printed circuit board or substrate such as, for example, the tank circuit portion of the printed circuit board or substrate of a voltage controlled oscillator (not shown) on which the resonator  320  is adapted to be seated and direct surface mounted, and side surfaces defining long side/longitudinal peripheral edges  328  and  330  and short side/transverse peripheral edges  332  and  334  respectively. 
     A plurality of elongate laser drilled through-holes defining conductive vias  336   a - m  ( FIGS. 5 and 6 ) extend through the body/interior of the substrate  322  and terminate in the top and bottom surfaces  324  and  326  respectively of the substrate  322 . Vias  336   a - m  extend through the substrate  322  in a generally normal relationship relative to the top and bottom substrate surfaces  324  and  326 . More specifically, it is understood that each of the vias  336   a - m  terminate in and define respective termination ends in respective portions of substrate surfaces  324  and  326 . Vias  336   a - m  are filled with the same type of conductive material as described above with respect to vias  36   a  and  36   b  of resonator  20  and thus the earlier description is incorporated herein by reference. 
     As shown in  FIGS. 5 and 6 , vias  336   a - f  extend in a spaced-apart and co-linear relationship along, spaced from, and adjacent to, long side substrate peripheral edge  328  while vias  336   g - l  extend in a spaced-apart and co-linear relationship along, spaced from, and adjacent to, opposed long side substrate peripheral edge  330 . Vias  336   a - f  and vias  336   g - l  are diametrically opposed to each other. Via  336   m  is generally centrally located on substrate  322 . 
     A total of seven solder spheres/balls  396   b ,  396   d,    396   f,    396   h,    396   j,    396   l , and  396   m  are secured to the bottom surface  326  of substrate  322  as shown in  FIG. 6 . Solder spheres  396   b ,  396   d ,  396   f ,  396   h ,  396   j , and  396   l  are seated over and secured to the respective filled ends of respective vias  336   b ,  336   d ,  336   f ,  336   h ,  336   j , and  336   l  terminating in substrate bottom surface  326 . In the embodiment shown, all of the respective solder balls/spheres overlying the respective termination ends of the respective vias  336  define respective ground pins adapted to be positioned in direct surface contact with the respective ground pads of an external printed circuit board (not shown) to which the resonator  322  is adapted to be direct surface mounted. 
     Solder ball/sphere  396   m  is located generally centrally along, spaced from, and adjacent to the short side substrate edge  334  and defines the input RF signal pin or pad of resonator  322  adapted for direct surface mount contact with the respective input RF signal pad of the external printed circuit board (not shown) on which the resonator  322  is adapted to be direct surface mounted. 
     Resonator  320  likewise comprises respective resonator strip patterns  342  and  344  ( FIGS. 5 and 6 ) defined on opposed substrate surfaces  324  and  326  respectively which have been formed thereon in a manner similar to that as described earlier with respect to the resonator strip pattern of resonator embodiments  20  and  220  above, the description of which is thus incorporated herein by reference. 
     As shown in  FIG. 5 , continuous, elongate resonator strip pattern  342  is generally curved and, more specifically, “serpentine”-shaped and includes respective spaced-apart, generally parallel, elongate, spaced-apart and straight serpentine strip segments/portions  342   a ,  342   b ,  342   c , and  342   d  which extend between and in a relationship generally spaced from and parallel to longitudinal side substrate edges  328  and  330 . Strip  342   a  is generally centrally located on the substrate surface  324  and defines a termination end  342   e  in electrical contact with and surrounding the end of via  336   m  which terminates in substrate surface  324 . Strip  342   d  overlies, and is in electrical contact with, the vias  336   g - 336   l  which extend along the longitudinal side substrate edge  330 . Strip  342   b  is located between strips  342   a  and  342   d . Respective curvilinearly-shaped segments  342   e ,  342   f , and  342   g  couple the straight segments  342   a ,  342   b ,  342   c  and  342   d  to each other. 
     The top substrate surface  324  additionally defines a separate elongate straight strip of conductive material  346  which extends along, is spaced from, and parallel to, the long side substrate edge  328  in a relationship overlying, and in electrical contact with, the ends of vias  336   a - 336   f  terminating in surface  324 . Strip segment  342   b  of resonator strip pattern  342  is positioned between strip  346  and strip  342   a  and strip  346  is positioned in diametrically opposed relationship to the strip segment  342   d  of serpentine strip pattern  342 . 
     As shown in  FIG. 6 , continuous, elongate resonator strip pattern  344 , which is positioned and oriented on surface  326  in a relationship diametrically opposed to resonator strip pattern  342  on surface  324 , is generally centrally located on bottom substrate surface  326 , is generally also curved and, more specifically, “serpentine”-shaped, and includes respective spaced-apart, generally parallel elongate serpentine straight segments/portions  344   a,    344   b,  and  344   c  all extending in a relationship generally parallel to long side substrate peripheral edges  328  and  330 . Respective curvilinearly-shaped segments  344   e  and  344   f  couple the straight serpentine segments  344   a,    344   b,  and  344   c  to each other. 
     Central serpentine segment  344   a  defines a terminal end  344   d  in electrical coupling relationship with and surrounding the end of central via  336   m  which terminates in the substrate surface  326  while outer serpentine segment  344   c  defines a terminal end or pad  344   e  in electrical coupling relationship with the sphere  396   m  disposed adjacent short side substrate edge  334 . 
     The bottom surface  326  still further defines a pair of additional elongate, generally straight strips of conductive material  348  and  350  which are separate (i.e., not electrically connected to) any of the strips of resonator strip pattern  344 . Strip  348  extends along and spaced from the long substrate side edge  328  in a relationship overlying the ends of the vias  336   a - 336   f  and in relationship spaced from and parallel to the strip  344   c  of resonator strip pattern  344 . Strip  350  is diametrically opposed to strip  348  and extends along the opposed long substrate side edge  330  in a relationship overlying the ends of the vias  336   g - 336   l  and in a relationship spaced from and parallel to the strip  344   b  of resonator strip pattern  344 .  FIG. 6  shows glasscoat layer  360 , similar to glasscoat layer  60  of resonator  20 , formed over the strip  344  and surface  326  of resonator  320 . 
     Thus, in accordance with this embodiment of the invention and referring to  FIGS. 5 and 6 , the RF signal is adapted to pass from the RF signal input pad on the printed circuit board of, for example, a voltage controlled oscillator (not shown) into and through the RF signal input/output solder sphere or pad  396   m  seated on bottom substrate surface  326 ; then through each of the strips  344   c,    344   b,  and  344   a  of serpentine resonator pattern  344  on bottom surface  326 ; then upwardly through the interior of substrate  322  and, more particularly, via  336   m;  then successively through each of the strips  342   a ,  342   b ,  342   c , and  342   d  of serpentine resonator pattern  342  on the top surface  324 ; then downwardly back through the interior of the substrate  322  through respective vias  336   g - 336   l;  then through respective solder spheres  396   h ,  396   j , and  396   l;  and then into the respective ground pads (not shown) of an oscillator printed circuit board. 
     As with the earlier resonator embodiments  20  and  220 , it is understood that the use of serpentine resonator strip patterns  342  and  344  on both surfaces  324  and  326  of resonator  320  in coupling relationship with respective through-hole vias advantageously defines an elongate and continuous conductive resonator transmission pathway/strip/pattern which makes resonator  320  particularly suitable and adapted for low frequency applications in the range below about 1.8 GHz. 
       FIGS. 7 and 8  depict a fourth resonator embodiment  420  in accordance with the present invention. 
     Initially, and as described earlier with respect to the resonator embodiments  20 ,  220 , and  320 , resonator  420  likewise initially comprises a generally rectangularly-shaped substrate or block  422  which preferably has the same dimensions and composition as the substrate  22  and thus the earlier discussion and description with respect to substrate  22  is hereby incorporated herein by reference. 
     Substrate  422  includes a top surface  424  ( FIG. 7 ), a bottom surface  426  ( FIG. 8 ) adapted to face the top of the printed circuit board (not shown) on which the resonator  420  is adapted to be seated and direct surface mounted, and side surfaces defining long side/longitudinal peripheral edges  428  and  430  and short side/transverse peripheral edges  432  and  434  respectively. 
     In a manner similar to resonator embodiment  220 , resonator  420  further includes a pair of elongate laser drilled through-holes defining conductive vias  436   a  and  436   b  which extend through the body/interior of the substrate  422  and terminate in respective apertures/openings in the top and bottom substrate surfaces  424  and  426 . Vias  436   a  and  436   b  extend through the substrate  222  in a generally normal relationship relative to the top and bottom substrate surfaces  224  and  226 . 
     In the embodiment of  FIGS. 7 and 8 , via  436   a  is generally centrally located and formed adjacent to and spaced from the short side substrate edge  432  while via  436   b  is generally centrally located and spaced from the short side substrate edge  434 . Vias  436   a  and  436   b  are co-linearly aligned and are filled with the same Ag/Pd material as described with respect to vias  36   a  and  36   b  of resonator  20  and thus the earlier description is incorporated herein by reference. 
     In a manner similar to resonator embodiment  220 , resonator  420  likewise includes conductive solder spheres/balls  450   a ,  450   b ,  450   c , and  450   d  similar in size and composition to spheres  50   a - 50   d  and  250   a - 250   d  positioned and secured on the bottom surface  426  of substrate  422  and thus the earlier description is incorporated herein by reference. Specifically, spheres  450   a ,  450   b , and  450   c  are aligned and extend along and adjacent the short side substrate edge  432  in a generally co-linear, spaced-apart relationship with sphere  450   b  overlying via  436   a . Sphere  450   d  is generally centrally located along opposed short side substrate edge  434  in a relationship diametrically opposed to and co-linear with sphere  450   b  and via  436   a.    
     Moreover, and as shown in  FIGS. 7 and 8 , each of the surfaces  424  and  426  of substrate  422  defines respective elongated conductive thick film resonator metallization pattern or strips  442  and  444  similar in composition to resonator metallization strips  42  and  44  of resonator  20  and resonator metallization strips  242  and  244  of resonator  220 , the description of the composition of each of such strips thus being incorporated herein by reference as though fully described except as otherwise described below. 
     Resonator strip  242  is generally straight and is defined by one end  442   a  which is located adjacent substrate short side edge  432  and surrounds and is electrically coupled to the aperture/end of via  436   a  terminating in substrate surface  424 ; a generally straight central body segment  442   b  extending away from via  236   b  in a relationship and orientation generally centered on substrate  422  and parallel to long side substrate edges  428  and  430 ; and an opposite end  442   c  which surrounds and is electrically coupled to the end/aperture of via  436   b  terminating in substrate surface  224 . 
     Resonator strip  444  on the bottom surface  426  of substrate  422  is generally curved and, more specifically, generally hook-shaped and is defined by one curvilinear proximal end  444   a  which surrounds and is electrically coupled to the sphere  450   d ; a generally straight segment  444   b  extending downwardly away from sphere  450   d  and proximal end  444   a  in a relationship and orientation generally parallel, adjacent to, and spaced from long side substrate edge  430 ; a curvilinearly-shaped base portion  444   c  disposed generally adjacent and spaced from substrate short side edge  432  and spheres  450   a - 450   c ; a straight portion/segment  444   d  which extends generally upwardly away from base portion  444   d  in a relationship spaced from, adjacent to, and generally parallel to long side substrate edge  428 ; and a terminal curvilinear end  444   e  which bends inwardly, surrounds, and is electrically coupled to the end/aperture of via  436   b  terminating in bottom surface  426 .  FIG. 8  shows glasscoat layer  460  similar to glasscoat layer  60  of resonator  20 , formed over strip  444  and surface  426  of resonator  420 . 
     Thus, in view of the above, and as explained above with resonator embodiments  20  and  220 , it is understood that the formation and use of elongate resonator strips  442  and  444  on opposed substrate surfaces  424  and  426  in coupling electrical relationship with respective vias  436   a  and  436   b  defines a continuous elongate RF signal transmission line/pathway/strip/pattern extending through the resonator  420  which makes the resonator  420  particularly suited and adapted for low frequency applications, i.e., applications in the range below about 1.8 GHz. 
     Moreover, in the resonator embodiment  420  of  FIGS. 7 and 8 , respective resonator strips  442  and  444 , as with the resonator strips  242  and  244  of resonator embodiment  220 , have a width which is generally about one quarter the width of the resonator  420  or about twice the width of each of the resonator strips  42  and  44  of resonator embodiment  20 . It is understood, of course, that increasing the width of the resonator strips results in a resonator with increased or heightened “Q” value since resistance decreases in proportion to an increase in the width of a conductive element. 
     In accordance with this embodiment of the invention and referring to  FIGS. 7 and 8 , the RF signal is adapted to pass successively from the RF input pad of, for example, the tank circuit of a voltage controlled oscillator (not shown) into and through either the solder sphere  450   b  or  450   d  which, depending upon the application, define respective RF signal input/output pads. In the application where the RF signal is inputted through the sphere  450   d , the RF signal passes in a generally clockwise direction through the length of resonator strip  444 ; then upwardly through the interior of substrate  422  through via  436   b ; then through the length of resonator strip  442  on top surface  424 ; and then back down and through the interior of board substrate  422  through via  436   a  into sphere  450   b  and into the RF signal output pad (not shown) of a printed circuit board. 
     It is still further understood that numerous variations and modifications of the embodiments described above may be effected without departing from the spirit and scope of the novel features of the invention. No limitations with respect to the specific resonator structures illustrated herein are intended or should be inferred. 
     For example, it is understood that resonator performance is a function of a variety of factors such as: the length of the resonator strips; the width of the resonator strips; the shape of the resonator strips; the number of resonator strips; the location and relationship and position of the resonator strips relative to one another; the location and relationship between the respective signal and ground tap points on the respective strips; the value of the dielectric constant of the ceramic substrate material; the thickness of the ceramic substrate material; the length, diameter, location and/or number of vias extending through the substrate material; and the distance between the lid and substrate surface. 
     Thus, it is understood that the invention is not limited to the particular resonator and ground strip patterns depicted herein but also to any and all such variations of these patterns, vias, etc., which may be necessary for a particular application.