Stencil opening on plated-through hole

ℹ️Help Zone Beautiful Boards
1

I am trying to create a board that utilizes THR-technology (that is, a THT part that is reflow-soldered). For this purpose, I require a stencil on the plated-through hole for printing on the solder paste. As I am using Sprint Layout, in order to get the openings in the SMD mask for the stencil I would have to place an SMD-Pad and then place a plated-through hole in the center of it, however this would technically count as via-in-pad, which you do not support.

My question is, how can I design my board so that when I order the boards and stencil through Aisler, I will have THT-plated through holes on the board, and an opening in the stencil to allow solder-paste to be printed over those plated-through holes? Ideally in a way that does not rate the board as complex.

2

Hi Alex,

Yes, unfortunately there doesn’t seem to be a proper way to create a custom stencil layer in Sprint layout.

We do not support filling/plugging vias with resin to prevent solder paste from flowing into the barrel of the via during reflowing, this is what we mean by via in pad. Unfortunately, this term can be understood differently, the electronics industry is not great at naming things :sweat: .

Could you provide me with an example of your workaround? I can take a look and see if its something we can process :slight_smile: .

Regarding the stencil, please note that we only provide stencils with a thickness of 100 µm.
This thickness is optimized for smaller components, for THR/ paste in pad you may need to create a rather large stencil aperture, to fully fill the trough hole, please take this into consideration.

3

Hi,

thanks for the quick response. Good to know about that definition of via-in-pad, you’re correct about the electronics industry and names…

Either way, should I just upload the project so you can take a look? I would prefer not to upload the layout file here in the forums.

Yes, I have tested the amount of solder paste required before, I usually use a larger rectangular cutout in the stencil around the round pth, relying on the capillary reaction to draw the solder to the hole, instead of the usual THR-method of filling the hole with paste.

4

Yes, you can upload it to our page and share the project ID with me I can take a look.

5

Project ID is GXGSFBBA

I am still optimizing copper distribution, so new revisions will be uploaded, but this should not affect the THR-considerations.

6

The stencil opening is there and we don’t flag any error, looks good. Could you share how you did it so other Sprint Layout users can benefit from it?

I will do some calculations regarding the stencil opening later.

7

Gladly. What I did was not that complicated.

  1. Place the plated-through holes, appropriate to the component you are trying to solder.
  2. Place one or more SMD-Pads, depending on the hole configuration of the part, on the plated-through holes, making sure there are no unwanted shorts.
  3. Remove the Soldermask-Opening marker on the SMD pads, so they won’t be bare.

This WILL essentially create copper planes around the holes, which in my applications is often desired for stability anyway, but care must be taken not to create unwanted shorts or copper planes.

I don’t know how to do it in a way that works for Aisler prototyping without creating copper planes, in general application I could create the SMD-Mask separately from the copper-top/copper-bottom layers and simply erase the SMD-pads afterwards, if desired.