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LMX2531 soldering NC pads

Mo.
Mastermind 22165 points
Other Parts Discussed in Thread: LMX2531

Hello Team,

One of my costumers is asking about soldering of specific pads on the LMX2531LQ1415E and LMX2531LQ1650E devices.
They have soldered pads 12, 13 and 39 according to older datasheet revisions. However, in the latest datasheet revision there has been a Layout example added with the remark that you should not solder these pads!

They have the following questions:

1. What happens if they keep soldering them? So far they have not experienced any problems.
2. Do they need to remove the copper pads below these pins? Or is it enough to just nor apply the solder paste?

Thank you in advance.

Kind regards,

Mo.

  • 0
    TI__Mastermind 28001 points

    Mo,

    This diagram is just for solder paste;  there should be copper on these unused pads.

    These unused pads are where the bondwires used to make the VCO tank inductance are connected.  The critical thing is that they are NOT grounded.

    As for putting solder paste where it says not to, I am not a soldering expert, but we have built PCB boards both ways and it has also worked fine.   The splitting up of the main ground plane is more important.

    The LMX2531 has an asymmetrical package footprint on the bottom and this is good reason to take care when soldering.  

    Regards

    Dean

  • 0 in reply to Dean Banerjee
    TI__Mastermind 22165 points
    Hi Dean,

    Thank you for the clarification.

    Kind regards,
    Mo.