[Moved]: Pads, bottom and top layer in PCB design

[DimaKilani]

Hello,

I'm a new candidate in PCB design. I'm using eagle software. I've done the symbol for capacitor and now want to do the foot print.
I'm using SMD which is surface mount pad to create the two terminals of the capacitors. This SMD has two layers only which are the bottom (red) and top (blue). I used top layer SMD to draw the terminals. I also drew a rectangle using bottom layer and put it on the top layer SMD to simplify routing. Now the question is: do I need to add the pad rectangle (green) on the capacitor terminals also? or the bottom/top layers are enough for the capacitor terminals?

Thanks.
Regards,
Dima

 

[andre_luis]

Regardless of the color settings of the CAD you are using, it seems you are confusing the things. If the component is for SMD assembly there should be no electrically connected primitives of the drawing on the opposite side.

 

[DimaKilani]

I cant get your point. Do you mean that I dont have to use the bottom layer? if yes, why?

- - - Updated - - -

SMD pad have only two layers top or bottom. For example, if I used the top layer, will that create the electrical connection? Do I need to use the pad rectangle (with the green color) to create that metal golden area on the PCB design?

 

[andre_luis]

The term SMD refers to "surface mount device", which means that for the footprint it is required just one side of the board to accomodate the component. If you need to connect something at the opposite side, this will be done during routing stage.

 

[DimaKilani]

Thanks for your reply. Now I got it and it does make sense. Will the SMD using the top layer for example creates a copper surface in the PCB? I know that the top layer is copper. Since I looked at different tutorials, I see people are using pads as shown in the attached figure which I think it creates copper surface. Do I really to add that rectangular pads to the top layer of the component as shown in the attached?

I'm a little bit confused since this is the first time am doing foot print.

 

[barry]

The top layer has copper pads. That's it. Your outline goes on the Silkscreen layer. You'll also need a paste mask and solder mask, but those are usually generated automatically by the software.

 

[DimaKilani]

Thanks for your replay. Yes, I activated the other layers and I noticed pad is covered by tStop and tCream.
That really helps

 

[Mattylad]

When you make a SMT component, do not ever use any bottom layer.

You should always make the component on the top side, even if it is intended to go on the bottom.
Then when you bring it into the design you simply move it onto the bottom side and everything that was on top gets mirrored onto the bottom instead.

Learn how the system works, what layer does what and what is required.
Also practice making some components, however get the "free" PCB library Expert Lite from pcblibraries.com as it will enable you to enter the component dimensions, it produces the footprint that you can then export to your chosen CAD system.

Google "Eagle layer list" and have a read of things like:
https://learn.adafruit.com/ktowns-u...-in-eagle-tutorial/creating-a-package-outline

Gogole how to make components in eagle, use Youtube.