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LM2990: TO-263 package Land Pattern possible incorrect

Renan Santos Adriano
Mastermind 22260 points
Part Number: LM2990

Hi Team,

My Customer seems to have an issue with a recommended "land pattern" for the LM2990S-5.0, TO-263 package. They followed our datasheet unfortunatley they are getting calls from the assembly house that the footprint will not solder correctly or meet IPC Class 3 requirements. The dimensions of the lead pads (not the case pad) are too short and not spaced far enough from the case pad for proper fit. Do you have any idea on this?

Regards,
_renan

  • 0
    TI__Mastermind 23361 points

    Hi Renan, 

    If you could provide the actual dimensions of the lead pads they measured, we can help to investigate if it is in a tolerated range and compare it to the "land pattern" recommended by the datasheet to see if there is an issue. Will you be able to get the measurements?

    Regards, 
    Jason Song

  • 0 in reply to Jason Song
    TI__Mastermind 22260 points

    Hi Jason,

    This is the reply from my customer. 

    "Our land pattern matches your datasheet exactly. The part doesn't meet IPC class 3 solder requirements. As an example, your datasheet calls for the three lead pads to be .085 long. The foot on the part is .078 which leaves no TOE and very little HEEL to meet the requirements. The overall of the part is .565 and across the land pattern is .600 which leaves .017 on each side, BUT you have to force the front of the leads off of the pad to get a proper HEEL."

    Regards,

    _Renan

  • 0 in reply to Renan Santos Adriano
    TI__Mastermind 37025 points

    Hi Renan,

    Many customers do not require a class 3 solder joint.  Class 3 solder joints are for designs which must go into high reliability designs, and the land patterns can take up more space.  The typical customer will want a class 2 solder joint, and rarely a class 1 solder joint.  I am not an expert on IPC-A-610 but we could try to locate someone in the business which knows more about these land patterns and how they were chosen, if that were necessary.  It sounds to me like the customer has a good idea of what land pattern they would need to meet their solder requirements.  When I worked at a previous company, we used class 3 solder joints for everything but there was a dedicated group that evaluated the land patterns and made sure they worked for our environments.  I would suggest to the customer to evaluate the land patterns of any component (even non-TI components) before using them, if they must use class 3 solder joints.

    Thanks,

    - Stephen