What is the purpose of this extra PCB pad?











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1
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I am looking to use this crystal in an upcoming design and I am a little bit confused by the datasheet.



The datasheet is available here:
CMR200T Datasheet



This is the image in question:
crystal_pads



Question:




  • What is the purpose of the large pad on the left? Should this be connected to my ground plane? I assume the two pins for the crystal are on the right.


Any help would be appreciated, thanks!






pcb-design grounding surface-mount crystal







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  • 2




    You solder the crystal case to it. See also: here.
    – jonk
    Dec 1 at 20:06

















up vote
1
down vote

favorite












I am looking to use this crystal in an upcoming design and I am a little bit confused by the datasheet.



The datasheet is available here:
CMR200T Datasheet



This is the image in question:
crystal_pads



Question:




  • What is the purpose of the large pad on the left? Should this be connected to my ground plane? I assume the two pins for the crystal are on the right.


Any help would be appreciated, thanks!






pcb-design grounding surface-mount crystal







share|improve this question


















  • 2




    You solder the crystal case to it. See also: here.
    – jonk
    Dec 1 at 20:06















up vote
1
down vote

favorite









up vote
1
down vote

favorite











I am looking to use this crystal in an upcoming design and I am a little bit confused by the datasheet.



The datasheet is available here:
CMR200T Datasheet



This is the image in question:
crystal_pads



Question:




  • What is the purpose of the large pad on the left? Should this be connected to my ground plane? I assume the two pins for the crystal are on the right.


Any help would be appreciated, thanks!






pcb-design grounding surface-mount crystal







share|improve this question













I am looking to use this crystal in an upcoming design and I am a little bit confused by the datasheet.



The datasheet is available here:
CMR200T Datasheet



This is the image in question:
crystal_pads



Question:




  • What is the purpose of the large pad on the left? Should this be connected to my ground plane? I assume the two pins for the crystal are on the right.


Any help would be appreciated, thanks!






pcb-design grounding surface-mount crystal




pcb-design grounding surface-mount crystal






share|improve this question













share|improve this question











share|improve this question




share|improve this question










asked Dec 1 at 20:06









Matt

132




132








  • 2




    You solder the crystal case to it. See also: here.
    – jonk
    Dec 1 at 20:06
















  • 2




    You solder the crystal case to it. See also: here.
    – jonk
    Dec 1 at 20:06










2




2




You solder the crystal case to it. See also: here.
– jonk
Dec 1 at 20:06






You solder the crystal case to it. See also: here.
– jonk
Dec 1 at 20:06












2 Answers
2






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3
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Primary reason is structural to prevent crystal mechanical shock and vibration damage or fatigue.



Since the Xtal is electrically isolated from the metal cylindrical case, it does not need an electrical gnd. It is just like the thru-hole parts with a wide can and very short leads where the can is electrically floating above the PCB surface.




  • If 0V grounded, the added sub-pF stray capacitance load might reduce the frequency of x ppm which may be in the range of your average load-cap tolerances.






share|improve this answer




























    up vote
    2
    down vote













    Many large pads like those are used as grounding points; you could solder the case to it, or you could leave it as is. It provides a point that you can use as a ground for later use. You will see alot of these in consumer electronics such as laptops; chassis points are often connected securely to the mobo ground, which is why you can use chassis as ground in most cases.



    Double check though, and test continuity using a DMM






    share|improve this answer





















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      2 Answers
      2






      active

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      2 Answers
      2






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      up vote
      3
      down vote













      Primary reason is structural to prevent crystal mechanical shock and vibration damage or fatigue.



      Since the Xtal is electrically isolated from the metal cylindrical case, it does not need an electrical gnd. It is just like the thru-hole parts with a wide can and very short leads where the can is electrically floating above the PCB surface.




      • If 0V grounded, the added sub-pF stray capacitance load might reduce the frequency of x ppm which may be in the range of your average load-cap tolerances.






      share|improve this answer

























        up vote
        3
        down vote













        Primary reason is structural to prevent crystal mechanical shock and vibration damage or fatigue.



        Since the Xtal is electrically isolated from the metal cylindrical case, it does not need an electrical gnd. It is just like the thru-hole parts with a wide can and very short leads where the can is electrically floating above the PCB surface.




        • If 0V grounded, the added sub-pF stray capacitance load might reduce the frequency of x ppm which may be in the range of your average load-cap tolerances.






        share|improve this answer























          up vote
          3
          down vote










          up vote
          3
          down vote









          Primary reason is structural to prevent crystal mechanical shock and vibration damage or fatigue.



          Since the Xtal is electrically isolated from the metal cylindrical case, it does not need an electrical gnd. It is just like the thru-hole parts with a wide can and very short leads where the can is electrically floating above the PCB surface.




          • If 0V grounded, the added sub-pF stray capacitance load might reduce the frequency of x ppm which may be in the range of your average load-cap tolerances.






          share|improve this answer












          Primary reason is structural to prevent crystal mechanical shock and vibration damage or fatigue.



          Since the Xtal is electrically isolated from the metal cylindrical case, it does not need an electrical gnd. It is just like the thru-hole parts with a wide can and very short leads where the can is electrically floating above the PCB surface.




          • If 0V grounded, the added sub-pF stray capacitance load might reduce the frequency of x ppm which may be in the range of your average load-cap tolerances.







          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered Dec 1 at 20:54









          Tony EE rocketscientist

          60.9k22192




          60.9k22192
























              up vote
              2
              down vote













              Many large pads like those are used as grounding points; you could solder the case to it, or you could leave it as is. It provides a point that you can use as a ground for later use. You will see alot of these in consumer electronics such as laptops; chassis points are often connected securely to the mobo ground, which is why you can use chassis as ground in most cases.



              Double check though, and test continuity using a DMM






              share|improve this answer

























                up vote
                2
                down vote













                Many large pads like those are used as grounding points; you could solder the case to it, or you could leave it as is. It provides a point that you can use as a ground for later use. You will see alot of these in consumer electronics such as laptops; chassis points are often connected securely to the mobo ground, which is why you can use chassis as ground in most cases.



                Double check though, and test continuity using a DMM






                share|improve this answer























                  up vote
                  2
                  down vote










                  up vote
                  2
                  down vote









                  Many large pads like those are used as grounding points; you could solder the case to it, or you could leave it as is. It provides a point that you can use as a ground for later use. You will see alot of these in consumer electronics such as laptops; chassis points are often connected securely to the mobo ground, which is why you can use chassis as ground in most cases.



                  Double check though, and test continuity using a DMM






                  share|improve this answer












                  Many large pads like those are used as grounding points; you could solder the case to it, or you could leave it as is. It provides a point that you can use as a ground for later use. You will see alot of these in consumer electronics such as laptops; chassis points are often connected securely to the mobo ground, which is why you can use chassis as ground in most cases.



                  Double check though, and test continuity using a DMM







                  share|improve this answer












                  share|improve this answer



                  share|improve this answer










                  answered Dec 1 at 20:16









                  QuickishFM

                  756




                  756






























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