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TPS54116-Q1: Question for cross-sectional shape of lead frame tip (TPS54116QRTWRQ1)

Junji Oro
Prodigy 50 points
Part Number: TPS54116-Q1

Tool/software:

Dear TI-technical engineer,

Our customer performed a physical analysis of a good sample of TPS54116QRTWRQ1.
When the cross section of the resin package was polished, erosion of the mold resin was found on the top surface of the lead frame tip. (Please see attach png image)
I checked the package drawing and found that the RTW0024N had erosion on the backside of the lead frame.
The erosion direction was not consistent when compared to the good analysis sample.

Question 1: Erosion of the mold resin was found on the top surface side of the lead terminal. Is this a normal structure?
Question 2: Maybe, are there any slits or dimple grooves on the top surface of the lead terminals that are not drawn on the package drawing?

Thank you.

Junji,

RTW0024N.pdf

  • 0
    TI__Guru* 80613 points

    Hi Junji,

    Can you provide a high resolution version of this photo? We have our packaging expert looking at this and he asked for this. Also his comments:

    "The top side etch at the saw line is not visible from the external view so that would be why it’s not on the drawing. That top notch feature improves adhesion of mold-leadframe."

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    Prodigy 50 points

    Hi Matt-san,

    The attached photo is taken with an optical microscope.
    It is difficult to provide a larger magnification than this.

    We need evidence to show our customers about this issue.
    If you have a design drawing of the top surface of the lead frame or a photo of the actual lead frame from the top surface, could you please provide it?
    Thank you.

    Junji,

  • 0 in reply to Junji Oro
    Prodigy 50 points

    Hi Matt-san,

    One more question.
    Customers want to know if there have been any changes in the topside etch for leadframes from the time of development to the present.
    If there have been any changes in the topside etch, could you please let us know the month and year of those changes?
    Thank you.

    Junji,

  • 0 in reply to Junji Oro
    TI__Guru* 80613 points

    Hi Junji,

    See the response from the packaging engineer:

    We do not share leadframe drawings. There have been no changes in the frame process or design.

    The top notch is intentional, below is a profile view of the space between units in the strip. You can see the saw line / package line and the resulting top notch feature after singulation. The mold aligns to the package line and everything inside the two blue lines is eliminated.

    He also mentioned that their solder joints are a little on the thin side also. He scaled the picture and estimates their solder joint thickness at 38 um. We want to see 50 um at minimum. The reason is BLR.

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    Prodigy 50 points

    Hi Matt-san,

    Thank you very much for providing the cross-sectional view.
    Customers would also like a top view of the lead frame.
    The attached diagram is an addition I drew below yours based on my guess, but does it represent the correct structure?

  • 0 in reply to Junji Oro
    TI__Expert 3745 points

    Our engineer for this thread is currently out of the office for the US Thanksgiving holiday. Responses will be delayed to week of December 1. Thank you for your patience.

  • 0 in reply to Sam
    TI__Guru* 80613 points

    Hi Junji,

    Please understand that we cannot share too many details on the leadframe design because we do not want to share propriety info. The info below is all we can share.

    This first image below is the top view of the structure between two units in the leadframe strip:

    The second image is the profile view of that area, rotated so that top is on top. You can see that the blue cut out region saws through the notches to yield a Top notch feature on the lead.

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    Prodigy 50 points

    Hi Matt-san,

    Thank you very much for your valuable information.
    The customer suspects that there have been changes to the lead frame design from the past.

    Please refer to the attached PDF file.
    The customer has received sample A from your company in 2022. They are comparing the lead side from that time with the current sample B in 2024. Their polished cross sections are obviously different, and the solder fillet angle is also slightly sharper.

    You said the other day that the lead frame has not changed its process and design since its development, is that correct?
    The customer would like to be informed and informed of any changes to the lead frame design. Thank you.

    C0DBAYY03274(TPS54116QRTWRQ1)_Package physical analysis.pdf