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SN74HCT245: About dimension of coplanarity

Part Number: SN74HCT245

Dear all,

I would like to ask about dimension of coplanarity in SN74HCT245NSR.

The figure below shows the outline of the SN74HCT245NSR.

Do the parts in red represent the coplanarity dimension?

I would appreciate it if you could get back to me right away.

Best Regards,


  • JEDEC defines seating plane as:

    (2) (of a surface-mounted device): The plane formed by the three terminal apexes that exhibit the greatest perpendicular distance from the package substrate, provided that the triangle formed by those three apexes encompasses the projection of the center of gravity (CoG) of the component.

    and coplanarity as:

    The condition where an interrupted surface, or two or more surfaces, have all their elements in one plane. The tolerance zone is established by two parallel planes between which all elements of the interrupted surface must lie. This is analogous to the flatness requirement for a continuous surface.

    NOTE See also "deviation from coplanarity".

    deviation from coplanarity:

    The distance between the intended contact point of a terminal and the established seating plane or regression plane.

    regression plane:

    A plane that (1) passes through the apex of the terminal that has the greatest perpendicular distance from the package substrate and (2) is parallel to the best-fit plane through the apexes of all terminals determined using the method of least squares.

    NOTE The regression plane may be used to emulate the package coplanarity during reflow soldering at the point of surface mounting.

    So, yes, this is the measure that you want.

  • Hi, Ladisch.

    Thank you for your reply.

    Your reply is very helpful for me.

    However, Our customer would like to request a response from a TI engineer or staff.



  • Hi Y.Ottey,

    Yes, Clemens is correct.