SparkFun Forums 

Where electronics enthusiasts find answers.

Questions relating to designing PCBs
By MCPorche
#180543
I have a simple question regarding creating a custom part in Ultiboard.

If I create a SMD 28 pin IC, I lay out the pads, and number then with Pin 1 in top left, Pin 14 at the bottom left, Pin 15 bottom right, and pin 28 top right.

If I create a 28 pin through hole DIP IC, do I number the pins the same? When I look at my through hole component in Ultiboard, am I looking at the top of the board? If so, do I need to place the pins on the bottom of the board? Or does Ultiboard base everything on where the component is actually located?

Thanks.
User avatar
By Ross Robotics
#180553
This is a PCB design forum. Your question is for the program itself. Best to ask the designer. But maybe someone has experience with this software, but this is the first time I've ever heard of it..
By MCPorche
#180558
I thought Multisim/Ultiboard were fairly well known programs. I guess I was wrong.

I also thought a PCB design forum was the appropriate place to ask a question about using PCB design software. I'll look for a different forum.

Thanks.
User avatar
By Ross Robotics
#180559
To answer your question though, most programs do look at the top of a component (unless it's been purposely placed on the bottom of a board).
By InactiveUser001
#180609
Yes, do it as you have described, you look at it through the top of the board.

Generally, If you make an SMT component, make it so that the pads are on the top of the board. Then when you use it you can change it to the bottom.

This way if it's on the top it's output in a placement report as being on top, if put on the bottom then it's on the bottom.

If you make the component with the pads on the bottom the system may assume the component is on the top unless you tell it that it's on the bottom (then the pads may swap to the top).
By davep238
#180704
MCPorche wrote:I have a simple question regarding creating a custom part in Ultiboard.

If I create a SMD 28 pin IC, I lay out the pads, and number then with Pin 1 in top left, Pin 14 at the bottom left, Pin 15 bottom right, and pin 28 top right.

If I create a 28 pin through hole DIP IC, do I number the pins the same? When I look at my through hole component in Ultiboard, am I looking at the top of the board? If so, do I need to place the pins on the bottom of the board? Or does Ultiboard base everything on where the component is actually located?

Thanks.
For all chips that I can think of, whether SMD or DIP, pin 1 is ALWAYS at the _bottom left_. Though I don't know anything about your PCB software, if you check existing chips in your libraries you should see that pin 1 _is_ at the bottom left. Pin numbering continues counter-clockwise. The highest pin # is at the upper left. So for your 28-pin chip, pin 14 is at the bottom right, pin 15 is at the upper right, and pin 28 is at the upper left.
HTH
By MCPorche
#180853
Ok, I wasn't clear. In my example, the chip was oriented vertically. I assume you had it horizontally.

But thanks for the info.
By InactiveUser001
#180856
If you follow I{PC7351 then pin 1 is top left.
See landpatterns.ipc.org/IPC-7351BNamingConvention.pdf

Although the std tries to force a common component orientation, the manufacturers of the components have not yet followed it.
I prefer to use the zero orientation of a component in the tape when presented to the placement machine (although this can sometimes change from supplier to supplier too).

Rotations can be a nightmare - whatever you choose - just be consistent throughout your library.

The PCB cad packages generally consider the zero rotation how the component is made - so make them at zero and then they take on other rotation values when you add them to a design.
By davep238
#180866
MCPorche wrote:Ok, I wasn't clear. In my example, the chip was oriented vertically. I assume you had it horizontally.

But thanks for the info.
I hadn't considered a vertical orientation. So now your numbering makes sense. Normally the orientation is horizontal.