Patent Publication Number: US-2020295726-A1

Title: Piezoelectric quartz crystal resonator

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional application of U.S. application Ser. No. 15/403,168, filed on Jan. 10, 2017, which is a Continuation Application of PCT Application No. PCT/CN2014/091108 filed on Nov. 14, 2014, which claims the benefit of Chinese Patent Application No. 201410566200.3 filed on Oct. 22, 2014, and the contents thereof are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present application relates to resonators, and more particularly to a piezoelectric quartz crystal resonator and a method for fabricating the same. 
     BACKGROUND OF THE INVENTION 
     A piezoelectric quartz crystal resonator generally has good frequency and temperature characteristics, however, in order to meet a higher requirement for a frequency stability, a frequency of the piezoelectric quartz crystal or an environmental temperature of the piezoelectric quartz crystal needs to be collected, and the frequency and temperature characteristics require corresponding compensations or corrections for meeting actual utilizing requirements. 
     In an existing piezoelectric quartz crystal resonator including a thermistor, the thermistor and a piezoelectric quartz crystal resonator piece are generally sealed in the same chamber, or the thermistor and the piezoelectric quartz crystal resonator piece are respectively sealed on an upper surface and a lower surface of a base board. The method of sealing the thermistor and the piezoelectric quartz crystal in the same chamber is prone to cause contamination of the piezoelectric quartz crystal and affect stabilities of resonator parameters. The method of sealing the thermistor and the piezoelectric quartz crystal on the upper surface and the lower surface of the base board respectively divides the chamber, however, it may increase the cost of a base seat; moreover, it may further increase the production cost because the assembly process requires special equipments. 
     SUMMARY OF THE INVENTION 
     The technical problem to be solved by the present invention is to provide a piezoelectric quartz crystal resonator and a method for fabricating the same, which are used to solve the problem in the prior art that sealing a thermistor and a piezoelectric quartz crystal resonator in the same chamber may cause contamination of the piezoelectric quartz crystal resonator. 
     The present invention is realized as follows: a piezoelectric quartz crystal resonator, comprising a circuit board, a quartz crystal resonator, and a thermistor; wherein, the thermistor is configured to detect a temperature of the quartz crystal resonator, the thermistor and the quartz crystal resonator are arranged on the circuit board and interconnected with each other via electric wires arranged on the circuit board; the thermistor and the quartz crystal resonator are sealed independently from each other by thermoplastic material, and the thermoplastic material sealing the thermistor is in contact with the thermoplastic material sealing the quartz crystal resonator. 
     Preferably, the thermistor and the quartz crystal resonator are arranged side by side on the same side of the circuit board, and a clearance is preset between the thermistor and the quartz crystal resonator. 
     Preferably, the thermistor is arranged on a back of the quartz crystal resonator, and at least one welding pad of the thermistor is connected with at least one welding pad of the quartz crystal resonator. 
     Preferably, a central portion of the circuit board where the quartz crystal resonator is arranged is provided with a through hole, and the thermistor is arranged in the through hole. 
     The present invention further provides a method for fabricating a piezoelectric quartz crystal resonator, which comprises the following steps: 
     Step A: arranging a plurality of design units on a circuit board, wherein each design unit includes a quartz crystal resonator and a thermistor, and a division clearance is preset between every two adjacent design units; 
     Step B: in each design unit, arranging at least one extension welding pad for the quartz crystal resonator at a bottom layer of the circuit board, and arranging at least one resonator welding pad configured to weld the quartz crystal resonator at a top layer of the circuit board; and at the same time, arranging at least one thermistor welding pad corresponding to the thermistor at the circuit board, wherein the thermistor welding pad is arranged at the same side of the circuit board as the resonator welding pad or the thermistor welding pad and the resonator welding pad are respectively arranged at opposite sides of the circuit board; 
     Step C: welding the quartz crystal resonator and the thermistor onto their corresponding welding pads respectively; 
     Step D: using thermoplastic material to seal the welded quartz crystal resonator and themistor independently from each other, wherein the thermoplastic material sealing the quartz crystal resonator is in contact with the thermoplastic material sealing the thermistor; 
     Step E: dividing the circuit board processed by the thermoplastic material according to the design units. 
     Preferably, when the thermistor is arranged at the same side of the circuit board as the quartz crystal resonator, the step C specifically includes the following sub-steps: 
     Sub-step C 01 : spreading solder paste on the welding pads of the circuit board, and attaching the quartz crystal resonator and the thermistor on their corresponding locations; 
     Sub-step C 02 : after the sub-step C 01 , performing reflow soldering for the circuit board, and removing scaling powder on the circuit board. 
     Preferably, when the thermistor and the quartz crystal resonator are respectively arranged at opposite sides of the circuit board, the step C specifically includes the following sub-steps: 
     Sub-step C 101 : forming a through hole in a central portion of each quartz crystal resonator on the circuit board, and arranging the welding pad of a corresponding thermistor at two ends of the through hole; 
     Sub-step C 102 : spreading solder paste on all resonator welding pads of the quartz crystal resonators on the circuit board, attaching the quartz crystal resonators on their corresponding locations, and performing reflow soldering to weld the quartz crystal resonators firmly; 
     Sub-step  103 : spreading solder paste on all thermistor welding pads of the thermistors arranged at another side of the circuit board, attaching the thermistors on their corresponding locations, performing reflow soldering to weld the thermistors firmly, and removing scaling powder from the circuit board; 
     Sub-step C 104 : injecting glue into each through hole, so that the glue fills clearances among the quartz crystal resonators, the thermistors, and the circuit board. 
     Preferably, in the step A, the plurality of design units are arranged into a matrix. 
     Compared with the prior art, the present invention has the following advantageous effect: the above-described piezoelectric quartz crystal resonator is shaped by resin injection molding after the quartz crystal resonators and the thermistors are arranged on the circuit board, so that each quartz crystal resonator has an independent chamber; thus, contamination of the quartz crystal resonators caused by the thermistors can be avoided, and the requirement for a higher frequency stability can be met. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a plurality of design units of a circuit board of a piezoelectric quartz crystal resonator fabricated by a method in accordance with a first embodiment of the present invention; 
         FIG. 2  is a schematic view of a matrix formed by the plurality of design units shown in  FIG. 1 ; 
         FIG. 3  is a schematic view of welding pads with solder paste spread thereon of the circuit board shown in  FIG. 2 ; 
         FIG. 4  is a schematic view of welding quartz crystal resonators and thermistors on the welding pads shown in  FIG. 3 ; 
         FIG. 5  is a schematic view of injection molding for the quartz crystal resonators and thermistors shown in  FIG. 4 ; 
         FIG. 6  is a schematic view of dividing the circuit with the quartz crystal resonators and the thermistors shown in  FIG. 5  into single quartz crystal resonators; 
         FIG. 7  is a disassembled schematic view of  FIG. 6 ; 
         FIG. 8  is a schematic view of a plurality of design units of a circuit board of a piezoelectric quartz crystal resonator fabricated by a method in accordance with a second embodiment of the present invention; 
         FIG. 9  is a schematic view of a matrix formed by the plurality of design units shown in  FIG. 8 ; 
         FIG. 10  is a schematic view of welding pads with solder paste spread thereon of the circuit board shown in  FIG. 9 ; 
         FIG. 11  is a schematic view of welding quartz crystal resonators on some welding pads shown in  FIG. 10 ; 
         FIG. 12  is a schematic view of welding quartz crystal resonators on others welding pads shown in  FIG. 10 ; 
         FIG. 13  is a schematic view of filling through holes shown in  FIG. 12  with glue; 
         FIG. 14  is a schematic view of dividing the circuit with the quartz crystal resonators and the thermistors shown in  FIG. 13 ; 
         FIG. 15  is a disassembled schematic view of  FIG. 14 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In order to make the objectives, technical solutions, and advantages of the present invention be clearer, the present invention will be further detailed below with reference to the accompanying drawings and embodiments. It should be understood that the embodiments described herein are only intended to illustrate but not to limit the present invention. 
     Referring to  FIG. 7  and  FIG. 15 , some embodiments of the present invention provide a piezoelectric quartz crystal resonator  100 , which includes a circuit board  103 , at least one quartz crystal resonator  101 , and at least one thermistor  102 . The thermistor  102  is configured to detect a temperature of the quartz crystal resonator  101 , the thermistor  102  and the quartz crystal resonator  101  are arranged on the circuit board  103  and interconnected with each other via electric wires arranged on the circuit board  103 , in particular, at least one welding pad  1011  of the quartz crystal resonator  101  is connected with at least one welding pad  1021  of the thermistor  102  via electric wires arranged on the circuit board  103 . The thermistor  102  and the quartz crystal resonator  101  are sealed independently from each other by thermoplastic material  104 , and a part of the thermoplastic material  104  that seals the thermistor  102  is in contact with a part of the thermoplastic material  104  that seals the quartz crystal resonator  101 , that is, the quartz crystal resonator  101  has an independent chamber. 
       FIGS. 1-7  show a first embodiment of the piezoelectric quartz crystal resonator  100 , wherein the thermistor  102  and the quartz crystal resonator  101  are arranged side by side on the same side of the circuit board  103 , and a clearance is preset between the thermistor  102  and the quartz crystal resonator  101 . 
       FIGS. 8-15  show a second embodiment of the piezoelectric quartz crystal resonator  101 , wherein the thermistor  102  is arranged on a back of the quartz crystal resonator  101 , and at least one welding pad  1021  of the thermistor  102  is connected with at least one welding pad  1011  of the quartz crystal resonator  101 . A central portion of the circuit board  103  where the quartz crystal resonator  101  is arranged is provided with a through hole  106 , and the thermistor  102  is fixedly arranged in the through hole  106 . 
     The present invention further provides a method for fabricating a piezoelectric quartz crystal resonator.  FIGS. 1-7  schematically show steps of a first embodiment of the method, and  FIGS. 8-15  schematically show steps of a second embodiment of the method. Each of the first and second embodiments comprises the following steps A to E, and the two embodiments differ from each other mainly in the steps A and C. 
     Step A: arranging a plurality of design units on a circuit board  103 , wherein each design unit includes a quartz crystal resonator  101  and a thermistor  102 , and a division clearance is preset between every two adjacent design units, as shown in  FIG. 1  or  FIG. 8 . Preferably, the plurality of design units can be arranged into a matrix, and an appropriate division clearance can be preset between every two adjacent design units, as shown in  FIG. 2  and  FIG. 9 . 
     Step B: in each design unit, arranging at least one extension welding pad for the quartz crystal resonator  101  at a bottom layer of the circuit board  103 , and arranging at least one resonator welding pad  1011  configured to weld the quartz crystal resonator  101  at a top layer of the circuit board  103 ; at the same time, arranging at least one thermistor welding pad  1021  corresponding to the thermistor  102  at the circuit board  103 , wherein the thermistor welding pad  1021  is arranged at the same side of the circuit board  103  as the resonator welding pad  1011  or the thermistor welding pad  1021  and the resonator welding pad  1011  are respectively arranged at opposite sides of the circuit board  103 . 
     Step C: welding the quartz crystal resonator  101  and the thermistor  102  onto their corresponding welding pads respectively. 
     Step D: using thermoplastic material  104  to seal the welded quartz crystal resonator  101  and themistor  102  independently from each other, wherein a part of the thermoplastic material  104  that seals the quartz crystal resonator  101  is in contact with a part of thermoplastic material  104  that seals the thermistor  102 . 
     Step E: dividing the circuit board  103  sealed by the thermoplastic material  104  according to the design units, so that each piezoelectric quartz crystal resonator  100  segmented from the circuit board  103  includes a thermistor  102  and a quartz crystal resonator  101 . 
     In the first embodiment of the method, the at least one welding pad  1011  of the quartz crystal resonator  101  and the at least one welding pad  1021  of the thermistor  102  are arranged at adjacent locations on the same side of the circuit board  103 . In particular, a bottom layer of the circuit board  103  can be provided with four welding pads, and the four welding pads can serve as extension welding pads of one quartz crystal resonator  101 . For example, the four welding pads can be a welding pad A, a welding pad B, a welding pad C, and a welding pad D respectively; the welding pad A is a first electrode of the quartz crystal resonator  101 ; the welding pad B is a grounded end, and is also connected with a second extension end of a thermistor  102 ; the welding pad C is a second electrode of the quartz crystal resonator  101 ; and the welding pad D is a first extension end of the thermistor  102 . A top layer of the circuit board  103  is provided with four resonator welding pads corresponding to a sealing location of the quartz crystal resonator  101 , and the four resonator welding pads are configured to weld the quartz crystal resonator  101 . Furthermore, in addition to the four extension welding pads A, B, C, and D and the four resonator welding pads, the circuit board  103  is further provided with two thermistor welding pads corresponding to a sealing location of the thermistor  102 , and the two thermistor welding pads are configured to weld the thermistor  102 . The welding pads on the top layer of the circuit board  103  are connected with the welding pads on the bottom layer of the circuit board  103  via electrically conductive and metallic via holes, as shown in  FIG. 1 . 
     When the first embodiment of the method is performed, the step C specifically includes the following sub-steps. Sub-step C 01 : spreading solder paste  105  on the welding pads of the circuit board  103  (comprising the welding pad  1011  of the quartz crystal resonator  101  and the welding pad  1021  of the thermistor  102 ), as shown in  FIG. 3 , and attaching the quartz crystal resonator  101  and the thermistor  102  on their corresponding locations. Sub-step C 02 : after the sub-step C 01 , performing reflow soldering for the circuit board  103 , and removing scaling powder on the circuit board  103 , as shown in  FIG. 4 . 
     In the second embodiment of the method, the at least one welding pad  1011  of the quartz crystal resonator  101  and the at least one welding pad  1021  of the thermistor  102  are respectively arranged at opposite sides of the circuit board  103 . In this embodiment, the thermistor  102  is arranged at a back of the quartz crystal resonator  101  and inside the circuit board  103 , as shown in  FIG. 8 . In particular, a bottom layer of the circuit board  103  can be provided with four welding pads, and the four welding pads can serve as extension welding pads of one quartz crystal resonator  101 . For example, the four welding pads can be a welding pad A, a welding pad B, a welding pad C, and a welding pad D respectively; the welding pad A is a first electrode of the quartz crystal resonator  101 ; the welding pad B is a grounded end, and is also connected with a second extension end of a thermistor  102 ; the welding pad C is a second electrode of the quartz crystal resonator  101 ; and the welding pad D is a first extension end of the thermistor  102 . A top layer of the circuit board  103  is provided with four resonator welding pads corresponding to a sealing location of the quartz crystal resonator  101 , and the four resonator welding pads are configured to weld the quartz crystal resonator  101 . At the same time, at least one of the four extension welding pads A, B, C, and D of the circuit board  103  is provided with a through hole  106 , and two thermistor welding pads  1021  are respectively arranged at two ends of the through hole  106  to assemble and weld the thermistor  102 . The welding pads on the top layer of the circuit board  103  are connected with the welding pads on the bottom layer of the circuit board  103  via electrically conductive and metallic via holes, and a thickness of the circuit board  103  is slightly larger than a thickness of the thermistor  102 , as shown in  FIG. 8 . 
     When the second embodiment of the method is performed, the step C specifically includes the following sub-steps: spreading solder paste  105  on all resonator welding pads  1011  of the quartz crystal resonators  101  on the circuit board  103 , attaching the quartz crystal resonators  101  on their corresponding locations, and performing reflow soldering to weld the quartz crystal resonators  101  firmly, as shown in  FIG. 11 ; spreading solder paste on all thermistor welding pads  1021  of the thermistors  102  arranged at another side of the circuit board  103 , attaching the thermistors  102  on their corresponding locations (e.g., attaching each thermistor  102  inside a corresponding through hole  106 ), performing reflow soldering to weld the thermistors  102  firmly, and removing scaling powder from the circuit board  103 , as shown in  FIG. 12 ; injecting glue into each through hole  106 , so that the glue fills clearances among the quartz crystal resonators  101 , the thermistors  102 , and the circuit board  103 . 
     The aforementioned piezoelectric quartz crystal resonator can be used in various conditions that require good frequency characteristics and high stabilities, for example, smart phones, smart terminals, Global Positioning System (GPS), and so on, and can also be used in temperature compensation quartz crystal oscillators or other electronic devices that require high frequency stabilities. 
     The aforementioned piezoelectric quartz crystal resonator ensures that each quartz crystal resonator thereof has an independent chamber, enables the thermistors thereof to collect temperatures of the quartz crystal resonators, and can meet the requirement for a higher frequency stability. Furthermore, adopting the fabricating method provided by the present invention can reduce fabrication cost and facilitate mass production. 
     What described above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent changes, and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.