How to create footprint for DPAK?

Layout
1

Hi everybody
I am creating footprint for MC33269dt3.3v (DPAK) case 369A but i don’t know how to calculate pin position,size,pad size and grid size etc.
Help please how math works i don’t know calculate.
[Uploading…]

2

Your question is unrelated to this thread and should be placed in another thread.

Did you look at the “Soldering Footprint” sketch on page 10 of the Datasheet?
http://www.onsemi.com/pub_link/Collateral/MC33269-D.PDF

Or, did you search the KiCAD libraries for either “DPAK”, or “TO-252”?

And, does your application require more heatsinking for this part than the basic pad size can provide?

Dale

3

Sorry if i made mistake to explain my question.
I need help about building custom footprint for mc33269_case369A-13 and other components. I would like to practices building .sch lib,.pretty etc.
If i am not wrong , for building footprints we need calculates pad size, pin size, pin position by math.

4

Normally you look in the datasheet.
as @dchisholm said above:
In the Datasheet on page 10 you can see all required measurements.
(mm and inches, be carefull what your settings are.)

The only thing to keep in mind is that normally the position of pads is relative to its center.
For this particular footprint i would create a pad of size 6.2x5.8mm at (0,0)

Two smd pads are placed at (6.68,±2.285) and have a size of 3x1.6mm
Details see drawing.

For the future:
it is much easier to help you if you have one question per thread. So please if you have a new unrelated question open a new topic.

1 Like
6

@TT_TECH

please stick to one topic per problem and don’t spam the forums.
Thanks for your understanding.

7

Thanks for helping :pensive:

8

Don’t be afraid do ask if you encounter further problems. :wink:

Designing good footprints is an art form. (This also extends to the pcb.)
In most cases it helps to make a simple drawing (Like the one i did above.)

I would also advice you to print out your finished footprint in scale 1:1 and check it against the part. (I have seen lots of errors which could have been prevented in this manner.)

9

Thank you very much :+1:

10

This is always a good idea.
Some printers do not print 100:100, but are usually better on the axis not involving paper thickness.
If you cannot fine-tune XY scales, two plots of 0’ and 90’, can give two good axes to check.

2 Likes
11

Thanks :upside_down:

12

And print an easy to test footprint like a dil16, for easy comparison and to check your printer calibration

13

I posted a DPAK-compatible footprint at Pad Holes Under SMT for Heat Sinking and other questions . Feel free to critique my work in that thread.

Dale