Patent Publication Number: US-2018054164-A1

Title: Structure of an integrated crystal oscillator package

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention: 
     The present invention relates to a structure of an integrated crystal oscillator package that has a first quartz crystal resonator, a second quartz crystal resonator, and an application-specific integrated circuit chip combined in a package. 
     2. Description of the Related Art: 
     Music players have been an important portion in smartphones. Some manufacturers even install an acoustic module from high-end players onto smartphones for better hi-fidelity (hi-fi) of the music. Such acoustic module has a quartz crystal resonator therein and a circuit designed to make use of the oscillation frequencies produced by piezoelectric effects to enhance the oscillation frequency of the quartz crystal resonator. Operations of such crystal oscillator package can be further divided into crystal resonator and crystal oscillator structures. 
       FIG. 1A  discloses a structure of a conventional crystal resonator package  10  which has a substrate  11 , a crystal resonator  12  mounted on the substrate  11  by silver glues  13 , and a cover  14  placed on the substrate  11 . Then referring to  FIG. 1B , two crystal resonators  10  are separately mounted on a PCB P of a smartphone to be operated by an integrated circuit (IC) thereon—to individually output a first clock rate and a second clock rate. Such structure is able to save the costs for parts in the manufacturing process and has a fair covering area on the smartphone and a fair integration of the different clock rates. However, the structure is unable to hold control of the phase noises produced in the process. 
       FIG. 1C  discloses another structure of a conventional crystal oscillator package  20  that has a substrate  21  with a staircase depression  211  and a stair surface  212 , an application-specific integrated circuit chip (ASIC)  22  disposed on the depression  211 , a crystal resonator  23  mounted on the stair surface  212  by silver glues  24 , and a cover  25  covered on the substrate  21 .  FIG. 1D  illustrates two of the crystal oscillators  20  mounted on a PCB P of a smartphone, each of which outputting a clock rate for operation. 
     In  FIG. 1E , a structure of another crystal oscillator package  30  is illustrated, including a substrate  31  with a first depression  311  thereon and a second depression  312  thereunder, a crystal resonator  32  mounted on the first depression  311  by silver glues  33 , and an application-specific integrated circuit chip (ASIC)  34  disposed on the second depression  312 , and a cover  35  placed above the first depression  311 .  FIG. 1F  further shows two of the crystal oscillator packages  30  mounted on a PCB P of a smartphone, each of which outputting a clock rate for operation. 
     The crystal oscillator package  20  and the crystal oscillator package  30  both are able to hold control of the phase noises and requires a fair area on a smartphone for installation; also, their integration function is satisfying. However, such structures require higher costs for parts in the manufacturing process. 
       FIG. 1G  shows a conventional codec C used for audio system on smartphones mentioned on the official website of Xiaomi Inc. (http://www.mi.com/minote/hifi/). It consumes lower costs but functions poorly in the phase noise performance. Then there is a hi-fidelity (hi-fi) system F developed to present much lower noises for better audio quality of the music as shown in  FIG. 1H , which was also mentioned on the website of Meizu Telecom Equipment Ltd (http://www.meizu.com/products/mx4pro/hifi.html). The hi-fi system F has two crystal oscillators  20 ,  30  combined with an isolated audio chip F 1 , an isolated amplifier F 2 , and other essential elements F 3  to achieve the purpose of better audio quality for music with low phase noises from the two independent crystal oscillators  20 ,  30 . Such structure has the installed PCB P setting up a CD sampling frequency as 44.1 kHz and a DVD sampling frequency as 48 kHz to process different audio formats. For further illustration, please see the chart below. 
     
       
         
           
               
               
               
             
               
                   
                   
               
               
                   
                 An audio format 
                   
               
               
                   
                 multiplied by 44.1 kHz 
                 An audio format multiplied by 
               
               
                   
                 corresponding to one 
                 48 kHz corresponding to the 
               
               
                   
                 of the crystal oscillators 
                 other of the crystal oscillators 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                  512 times 
                 22.5792 MHz 
                 24.576 MHz 
               
               
                 1024 times 
                 45.1584 MHz 
                 49.152 MHz 
               
               
                 2048 times 
                 90.3168 MHz 
                 98.304 MHz 
               
               
                   
               
            
           
         
       
     
     From the chart we can learn that the frequencies multiplied by the sampling frequencies can also apply to the structures. 
     On the other hand, as shown in  FIG. 11 , the hi-fi system F requires two crystal oscillators; that is, the system needs connecting points for two isolated electricity power suppliers VDD, two ground connections GND, two signal input controllers INH, and two connecting points F out for frequency output. The input frequency of the system has to be switched between the signal input controllers INH for operation. In other words, such structure is not integrated. 
       FIG. 1J  is disclosed in Japanese Patent No. 3770607. There is an integrated downsized crystal resonator package  40 , including an insulating substrate  41  having an oblong depression  411 , a first stair surface  412 , and a second stair surface  413 , a first electrode pad  42  disposed on the first and second stair surfaces  412 ,  413 , a second electrode pad  43  disposed on the first and second stair surfaces  412 ,  413 , a wiring conductor  44  arranged under the substrate  41  and electrically connected to the first and second electrode pads  42 ,  43 , and a cover  45  disposed on the substrate  41 . The crystal resonator package  40  thereby has a first crystal resonator  47 A and a second crystal resonator  47 B respectively mounted on the first and second electrode pads  42 ,  43  by a conductive adhesives  46 . The package volume is therefore downsized. 
       FIG. 1L  shows another downsized crystal resonator package  50  with airtight sealing disclosed in Japanese Patent No. 5882868. The package includes an insulating substrate  51  with a first depression  511  thereon connecting a second depression  512  thereunder via a through hole  513 , a first wiring conductor  52  disposed in the first depression  511 , a second wiring conductor  53  disposed in the second depression  512 , a second crystal resonator  54 B bonded to the second wiring conductor  53  by a bonding material  55 , a second cover  56  sealing the second depression  512 , a first crystal resonator  54 A bonded to the first wiring conductor  52  by the bonding material  55 , and a first cover  57  sealing the first depression  511 . The first and second depressions  511 ,  512  are vacuumed via the through hole  513  to be airtight. The package volume is therefore downsized as well. 
     The package structures disclosed above mentioned nothing about hi-fi systems for musics. However, if they are applied to be mounted on a PCB for outputting different clock rates, there is still a problem of phase noises control. 
     All in all, the question is how to sustain a structure with two crystal oscillators that satisfies requirement of hi-fi system with low phase noises and meanwhile keeps the features of less volume and better integration; also, the costs for parts is another subject to be improved. 
     SUMMARY OF THE INVENTION 
     A primary object of the present invention is to provide an integrated crystal oscillator package that holds control of phase noises to satisfy a hi-fi quality, keeps features of less area for installation of a circuit on smartphones and integration of different frequencies output from different clock rates, and reduces costs for parts in the manufacturing process. 
     To achieve the objects mentioned above, the present invention comprises a package including a substrate and cover, said substrate having a staircase depression with a first stair surface and a second stair surface, said first stair surface further having a first conductive section and said second stair surface further having a second conductive section, a third conductive section being arranged at a bottom of the staircase depression; a first quartz crystal resonator having an end thereof fixed on the first conductive section; a second quartz crystal resonator having an end thereof fixed on the second conductive section; and an application-specific integrated circuit chip (ASIC) combined on the third conductive section, said third conductive section further individually connected to the first and second conductive sections; whereby the ASIC has a switch control for operation when receiving audio formats with different degree of hi-fidelity (hi-fi) corresponding to a first clock rate output from the first quartz crystal resonator or to a second clock rate output from the second quartz crystal resonator. 
     Furthermore, frequencies of 44.1 kHz and a multiple thereof are corresponding to the first clock rate, and frequencies of 48 kHz and a multiple thereof are corresponding to the second clock rate. The first and second quartz crystal resonators have either the same sides or opposite sides fixed on the first and second conductive sections. 
     The substrate is a ceramic substrate or a PCB to have electric wires arranged therein separately connecting the third conductive section with the first and second conductive sections for the switch control to operate. The substrate further has a first bond pad group and a second bond pad group at a bottom thereof, said first and second bond pad groups individually coupled to the ASIC via the electric wires for the present invention to form a surface mount device (SMD). 
     The switch control has a first switch and a second switch to switch between a first sampling frequency output and a second sampling frequency output and to simultaneously output both frequencies. 
     With structures disclosed above, the present invention has the first quartz crystal resonator, the second quartz crystal resonator, and the ASIC combined in a package to form an integrated package structure that includes two isolated circuits and an isolated ASIC, so as to control the phase noises to achieve requirements of the hi-fi system and to ensure the package uses a minimum area on a smartphone with the feature of integration of different clock rates. In addition, the present invention consumes lower costs for parts in the manufacturing process. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a schematic diagram illustrating a structure of a conventional crystal resonator; 
         FIG. 1B  is a schematic view of two conventional crystal resonators mounted on a PCB; 
         FIG. 1C  is a schematic diagram illustrating a structure of a conventional crystal oscillator; 
         FIG. 1D  is a schematic view of two conventional crystal oscillators mounted on a PCB; 
         FIG. 1E  is a schematic diagram illustrating a structure of another conventional crystal oscillator; 
         FIG. 1F  is a schematic view of two conventional crystal oscillators in  FIG. 1E  mounted on a PCB; 
         FIG. 1G  is a schematic view of a conventional codec; 
         FIG. 1H  is a schematic view of a conventional high-fidelity (hi-fi) system; 
         FIG. 1I  is a schematic view of a conventional hi-fi system with a package of two crystal resonators; 
         FIG. 1J  is a schematic diagram illustrating a structure of a downsized crystal resonator package according to the prior art; 
         FIG. 1K  is a schematic diagram showing the downsized crystal resonator package mounted on a PCB; 
         FIG. 1L  is a schematic diagram illustrating a structure of a downsized crystal resonator package with airtight sealing according to the prior art; 
         FIG. 1M  is a schematic diagram showing the downsized crystal resonator package with airtight sealing mounted on a PCB; 
         FIG. 2  is a perspective view of the present invention; 
         FIG. 3  is a sectional view along line  3 - 3  in  FIG. 2 ; 
         FIG. 4  is another sectional view of the present invention; 
         FIG. 5  is a schematic diagram illustrating the present invention mounted on a PCB; 
         FIG. 6A  is a circuit diagram of the present invention; and 
         FIG. 6B  is an application example of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIGS. 2-6B , in a preferred embodiment, an integrated crystal oscillator package  60  comprises a package  70 , a first quartz crystal resonator  80 A, a second quartz crystal resonator  80 B, and an application-specific integrated circuit chip (ASIC)  90 . 
     The package  70  includes a substrate  71  and cover  72 . The substrate  71  has a staircase depression  73  with a first stair surface  74  and a second stair surface  75 ; the first stair surface  74  further has a first conductive section  741  and the second stair surface  75  further has a second conductive section  751 , and a third conductive section  731  is arranged at a bottom of the staircase depression  73 . In this embodiment, the substrate  71  is a ceramic substrate or a PCB to have electric wires (not shown) arranged therein, and the first, second, and third conductive sections  741 ,  751 ,  731  have a plurality of connecting points. 
     The first quartz crystal resonator  80 A has an end thereof fixed on the first conductive section  741  on the first stair surface  74 , and the second quartz crystal resonator  80 B has an end thereof fixed on the second conductive section  751  on the second stair surface  75 . Referring to  FIGS. 3 and 4 , in this embodiment the first and second quartz crystal resonators  80 A,  80 B may have their fixed ends either on the same sides or at opposite sides. Furthermore, the first and second quartz crystal resonators  80 A,  80 B are respectively coupled to the first and second conductive sections  741 ,  751  via the connecting points thereof, and the package  70  has the first and second quartz crystal resonators  80 A,  80 B airtight sealed therein. 
     The ASIC  90  is disposed on the third conductive section  731  of the staircase depression  73 , and the third conductive section  731  is individually connected to the first conductive section  741  of the first stair surface  74  and the second conductive section  751  of the second stair surface  75 . In this embodiment, the ASIC  90  is coupled to the connecting points of the third conductive section  731  and has the electric wires arranged therein to connect the third conductive section  731  with the first and second conductive sections  741 ,  751  for the ASIC  90  to be separately connected to the first quartz crystal resonator  80 A and the second quartz crystal resonator  80 B. In addition, the substrate  71  further has a first bond pad group  711  and a second bond pad group  712  at a bottom thereof, and the first and second bond pad groups  711 ,  712  are individually coupled to the ASIC  90  via the electric wires for the present invention to become a surface mount device (SMD). 
     In  FIG. 5 , the integrated oscillator package  60  is mounted on a PCB P of a smartphone. In this application, the ASIC  90  has a switch control  91  to switch between different audio formats with different degree of hi-fidelity (hi-fi) to individually corresponds to a first clock rate  92  output from the first quartz crystal resonator  80 A and to a second clock rate  93  output from the second quartz crystal resonator  80 B, so as to form a structure of an integrated crystal oscillator package. In this embodiment, the switch control  91  has a first switch  911  and a second switch  912  to switch between the first clock rate  92  and the second clock rate  93  for output, or to simultaneously output both frequencies. 
       FIG. 6A  illustrates a circuit diagram of the present invention. Normally a hi-fi system requires two crystal oscillators; in other words, there are isolated connecting points for two electricity power suppliers VDD, two ground connections GND, two signal input controllers INH, and two frequency outputs F. However, in the present invention the crystal oscillators are integrated into one single package which only requires connecting points for one electricity power supplier VDD, one ground connection GND, one signal input controller INH, one first clock rate output FA, one second clock rate output FB, and one switch transmission input FS. That is, the present invention is highly integrated to have two crystal oscillators and one ASIC within one package. In this embodiment, the audio formats are 44.1 kHz and 48 kHz. The first clock rate  92  outputs a 44.1 kHz frequency and the second clock rate  93  outputs a 48 kHz frequency. Further referring to  FIG. 6B , the first and second crystal quartz resonators  80 A,  80 B can individually output the frequency or simultaneously output both frequencies in operation; the first clock rate  92  outputs a frequency of 44.1 kHz or a multiple thereof, and the second clock rate  93  outputs a frequency of 48 kHz or a multiple thereof. 
     To further elaborate features of the present invention, please see the following chart for comparison. 
     
       
         
           
               
               
            
               
                   
                   
               
               
                   
                 Item 
               
            
           
           
               
               
               
               
               
            
               
                   
                 A 
                 B 
                   
                   
               
               
                   
                 Conventional 
                 Conventional 
                 C 
                 D 
               
               
                   
                 package 
                 package 
                 Conventional 
                 Integrated 
               
               
                   
                 structure of 
                 structure of 
                 integrated 
                 package of 
               
               
                   
                 two crystal 
                 two crystal 
                 package of two 
                 crystal 
               
               
                   
                 resonators 
                 oscillators 
                 crystal 
                 oscillators 
               
               
                   
                 (FIGS. 
                 (FIGS. 
                 resonators 
                 (the present 
               
               
                   
                 1A-1B) 
                 1C-1F) 
                 (FIGS. 1J-1M) 
                 invention) 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                 Quality 
                 Excellent 
                 Excellent 
                 Excellent 
                 Excellent 
               
               
                 factor 
               
               
                 Phase noise 
                 Poor 
                 Excellent 
                 Poor 
                 Excellent 
               
               
                 control 
               
               
                 Integration 
                 Fair 
                 Fair 
                 Excellent 
                 Excellent 
               
               
                 of different 
               
               
                 clock rates 
               
               
                 Covering 
                 Fair 
                 Fair 
                 Less 
                 Less 
               
               
                 area on a 
               
               
                 smartphone 
               
               
                 Costs for 
                 Fair 
                 High 
                 Low 
                 Fair 
               
               
                 parts 
               
               
                   
               
            
           
         
       
     
     As the control of phase noises is a vital factor in hi-fi system, items A and C are ruled out undoubtedly. The present invention further integrates the crystal oscillators with an ASIC as a package to retain the features of excellent quality of phase noise control to satisfy the requirements of hi-fi systems and meanwhile keep the features of better integration and less covering area on a smartphone, therefore reducing the costs for parts as well. 
     In short, the present invention integrates the first and second crystal quartz resonators  80 A,  80 B and the ASIC  90 , and keeps the feature of better phase noise control to achieve and satisfy the requirements of hi-fi systems; such structure also consumes lower costs for parts in the manufacturing process. 
     Although a particular embodiment of the invention has been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except by the appended claims.