Questions on vias, stop masks and sparkfun lib's 1x08 header

Community PCB Design
1

Sorry if some of these questions may sounds basic.

My understanding of stop masks is that they will prevent anything from convering the pad they are covering, including preventing silk screen or anything, This is important for access to the pads, correct me if I’m wrong.

But why are they required for Vias? A via doesn’t need access from the top-level, it just has to connect signals across layers, right.

I’m asking this because I’m getting a warning with Eagle DRC when I have things placed above my Via (via has an automatically added Stop mask), such as another IC.

In this case, I guess if Vias didn’t have that stop mask automatically added, I would get no errors. Why are those stop masks auto-added on Vias by Eagle?

Second question, What’s the difference between a “Drill” and a “Hole” in Eagle terms? I see the 1x08 adds a Drill component on each pin, do I need to also add a Hole?

Third question, so I’m using the 1x08, and plan to use it with breakaway 0.1" headers. Should the pins be facing one side of the board, while the pads placed on the other side? Or do the pins and the pads go onto the same side?

Thanks in advance,

Joel Fernandes

2

  1. if the STOP layers are turned off when you run DRC, then you won’t get the DRC stop mask errors.

  2. A “drill” indicates a hole that will be plated with copper that a component lead will be inserted. A “drill” is also used for vias. A “hole” is just used for mounting holes, standoffs, screws etc. A component lead is never inserted into a “hole”. So, no you do not need to add “holes” to the header.

  3. For through hole parts, such as your header, the part is mounted on the Top side of the board and the pins are soldered to the pads on the Bottom side of the board. If the board is double sided (copper on both sides), then there will be pads on both sides of the board. The copper on one side is connected to the copper on the other side with plated holes. Thus electrically it doesn’t matter which side the component is mounted on. However, I’ve never seen through-hole parts (i.e. resistors) mounted on the bottom of a board. Connectors, on the other hand, may be mounted on either the top or bottom of the board.

3

Thanks so much for the reply. I understood 2) and 3) fully, that really helped.

For 1), actually I am going to be putting solder mask on my board, so I think I would like to keep the stop masks enabled.

I am just wondering- why do vias come with a default stop masks in Eagle? Say for example, if the via doesn’t have a stop mask, then I guess- AIUI - the via will be covered with solder mask. which means I wont be able to access it on the top pads. But that should OK because I don’t need to access them from the top, right?

Infact not having stop masks on Vias is probably a good thing, as it would prevent accidental access to the via, right?

Thanks!

Joel Fernandes

4

I think you have it backwards. Vias have a stop mask layer applied to them by default. This means that there is no stop mask covering them when the board is made. If you don’t need access to the via (i.e. for testing) then you need to uncheck the stop mask box. I know it’s confusing…

Summary: Under via properties

checked = not covered

unchecked = covered

If you have a lot of vias that need to be covered, you can use the change tool.