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LM2940-N: The MSL level difference between LM2940T-5.0/NOPB and LM2940T-5.0/LF08

Shinichi Inoue
Guru 20896 points
Part Number: LM2940-N

Dear Specialists,

My customer'd like to know the MSL level difference between LM2940T-5.0/NOPB and LM2940T-5.0/LF08.

I would be grateful if you could advise.

---

LM2940T-5.0/NOPB and LM2940T-5.0/LF08 are the same TO220 package.

Package drawing are almost the same. Accrding to the following thread, LM2940T-5.0/LF08 is straight lead.

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/895406/lm2940-n-package-drawing

On the other hand, MSL level is different.

LM2940T-5.0/NOPB is MSL1 and LM2940T-5.0/LF08 is MSL3.

Could you please let us know the reason.

---

I appreciate your great help in advance.

Best regards,

Shinichi

  • 0
    TI__Genius 12535 points

    Hello Shinichi, 

    MSL ratings are determined based on the materials used for the Leads and the packaging. Based on the BOM materials, the MSL qualification is determined, hence the difference between the two. 

    Best, 

    Edgar Acosta

  • 0 in reply to Edgar Acosta1
    Guru 20896 points

    Hi Edgar,

    Thank you for your reply.

    I checked the material composition of the two devices, it was exactly the same.

    LM2940T-5.0/NOPB

    https://www.ti.com/quality-reliability-packaging-download/report?opn=LM2940T-5.0/NOPB

    LM2940T-5.0/LF08

    https://www.ti.com/quality-reliability-packaging-download/report?opn=LM2940T-5.0/LF08

    Could you please let us know what is the reason for the different MSL levels?

    I appreciate your great help and cooperation.

    Best regards,

    Shinichi

  • 0 in reply to Shinichi Inoue
    TI__Genius 12535 points

    Hi Shinichi, 

    I am currently digging further into this. I will get back to you as soon as possible. 

    Best, 

    Edgar Acosta

  • 0 in reply to Edgar Acosta1
    Guru 20896 points

    Hi Edgar,

    Thank you for your reply.

    I'm looking forward to waiting your suggestion.

    I appreciate your great help and cooperation.

    Best regards,

    Shinichi

  • 0 in reply to Shinichi Inoue
    TI__Genius 12535 points

    Hi Shinichi, 

    I appreciate the patience. I will respond once I obtain more information. Please give a few days, specially since this is an older product and it does take some time to find more information. 

    Best, 

    Edgar Acosta

  • 0 in reply to Edgar Acosta1
    Guru 20896 points

    Hi Edgar,

    Thank you for your reply.

    I understand.

    I'm looking forward to waiting your survey result.

    I appreciate your great help and cooperation.

    Best regards,

    Shinichi

  • 0 in reply to Shinichi Inoue
    TI__Genius 12535 points

    Hi Shinichi, 

    I apologize for the delayed response. The team is still looking into this. However, as a brief overview, this part is one of our older products that belonged to National Semiconductors. When the device was qualified, it seems like it was done based of another similar package and device that was MSL 1 at the time. 

    This is something that we are still investigating, but this seems to be part of the problem. 

    Best, 

    Edgar Acosta

  • 0 in reply to Edgar Acosta1
    Guru 20896 points

    Hi Edgar,

    Thank you for your reply.

    I understand the situation.

    Could you please provide when you obtain more information. 

    As you know, the delivery time of the device is very long.

    Customers are considering whether LM2940T-5.0/LF08 can be used instead of LM2940T-5.0/NOPB, this point should be clarified.

    I appreciate your great help and cooperation.

    Best regards,

    Shinichi

  • 0 in reply to Shinichi Inoue
    TI__Genius 12535 points

    Hi Shinichi, 

    Thank you for the patience. 

    I am waiting for further information from Quality team. I will get back to you as soon as I get a response. 

    Best, 

    Edgar Acosta

  • 0 in reply to Edgar Acosta1
    TI__Genius 12535 points

    Hi Shinichi, 

    Both devices should have same MSL rating, since both have minor differences between the drawings (NEB and NDE) and they have same BOM. 

    They should have MSL1 since they are legacy devices. We will keep on working to determine why they have different MSL ratings and fix it on our end.

    Once again thank you for the patience. 

    Best, 

    Edgar Acosta

  • 0 in reply to Edgar Acosta1
    Guru 20896 points

    Hi Edgar,

    Thank you for your devoted support.

    I'm looking forward to waiting your survey result.

    I appreciate your great help and cooperation.

    Best regards,

    Shinichi

  • 0 in reply to Shinichi Inoue
    TI__Genius 12535 points

    Hi Shinichi,

    LM2940T-5.0/LF08 has formed lead whereas LM2940T-5.0/NOPB is in straight lead.

    Formed lead has mechanical stress which might impact the packaging MSL level classification, this is similar to TO263 surface mount package which is classified as MSL3.

    Straight lead has no mechanical stress impact and hence classified as MSL1.

    Best, 

    Edgar Acosta

  • 0 in reply to Edgar Acosta1
    Guru 20896 points

    Hi Edgar,

    Thank you for your reply.

    As I said from the beginning, the dimensions of the LM2940T-5.0 / LF08 look exactly the same as the LM2940T-5.0/ NOPB.

    Furthermore, the material composition is the same.

    On the other hand, LM2940T-5.0/ LF08 is classified as lead-formed.

    I think this is the only reason why LM2940T-5.0/LF08 is MSL3.

    Why is the LM2940T-5.0 / LF08 classified as Read Formed even though it is not lead formed?

    Is this device intended for lead-form at the customer?

    I appreciate your great help and cooperation.

    Best regards,

    Shinichi

  • +1 in reply to Shinichi Inoue
    TI__Genius 12535 points

    HI Shinichi, 

    Even though the material compositions are similar and that the device packaging are similar, there is a slight difference. Notice in the following image how the leads are not straight: 

    This is the NEB package (LM2940T-5.0 / LF08). This creates a mechanical stress, hence, creating the possibility for moisture formation, hence the MSL 3 rating. 

    Now if we look at the NDE package:

    Notice it has straight leads, this is LM2940T-5.0/ NOPB and this is MSL1. 

    Thank you for the patience. 

    Best, 

    Edgar Acosta

  • 0 in reply to Edgar Acosta1
    Guru 20896 points

    Hi Edgar,

    Thank you for your reply.

    According to the thread below, LM2940T-5.0/LF08 is straight lead.

    Could you please confirm.

    RE: LM2940-N: The MSL level difference between LM2940T-5.0/NOPB and LM2940T-5.0/LF08

    This image is a cut from the thread.

    I thought LM2940T-5.0/LF08 is straight lead.

    Which is correct  straight or lead formed ?

    Could you please let us know.

    I appreciate your great help and cooperation.

    Best regards,

    Shinichi

  • 0 in reply to Shinichi Inoue
    TI__Genius 12535 points

    Hi Shinichi, 

    I believe you attached this same thread in your last response. 

    However, LM2940T-5.0/LF08 is formed lead and LM2940T-5.0/NOPB is straight lead. This is shown on the Mechanical Data for each package and this was confirmed with conversations with the Quality team. 

    As to why the CAD drawings do not reflect this, I would have to dig deeper. But as far as why one is MSL1 and the other is MSL3, the answer relies on this mechanical stress since this creates a possible moisture path into the package. 

    Best, 

    Edgar Acosta

  • 0 in reply to Edgar Acosta1
    Guru 20896 points

    Hi Edgar,

    Thank you for your reply.

    I was really surprised the LM2940T-5.0/LF08 is lead-formed. Is it correct?

    If so, I have to inform the customer because they're considering LM2940T-5.0/LF08 instead of LM2940T-5.0/NOPB.

    The E2E thread is wrong I showed.

    Also the product folder and CAD data on the HP should be modified soon.

    Or some people will misunderstand.

    On the other hand, I understand the difference in MSL levels.

    I appreciate your great help and cooperation.

    Best regards,

    Shinichi

  • +1 in reply to Shinichi Inoue
    TI__Genius 12535 points

    Hey Shinishi, 

    Yes, LM2940T-5.0/LF08 is lead-formed. 

    I will see on our end to get the CAD data and HP corrected to avoid future confusions. 

    Best, 

    Edgar Acosta

  • 0 in reply to Edgar Acosta1
    Guru 20896 points

    Hi Edgar,

    Thank you for your reply.

    I asked the customer to stop considering the LM2940T-5.0/LF08.

    CAD data and HP information should be corrected as soon as possible.

    The E2E thread is misleading and should be fixed or deleted.

    https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/895406/lm2940-n-package-drawing

    I appreciate your great help and cooperation.

    Best regards,

    Shinichi