hi,
at this point i came across pcb’s that required to use the wave soldering the pcb due to some higher quantity of through hole components.
search through the net but did not find any topic that talks about adhesive stencil.
is there any simple steps to generate the adhesive gerber for stencil, or some plugins ??
Thanks,
KiCad does have layers for adhesive:
But there is very little about it in the PCB manual. I guess the intended use is to use aperture pads in your footprints on the adhesive layer for your glue dots.
It also triggers some old memory. If you use SMT resistors with for example 0805 size and want to draw a track under it. you can have troubles with the adhesive layer. Because of the thickness of the track, the adhesive dot gets squished (squashed?) more, which results in a bigger gluing surface, and this may interfere with the pads.
The adhesive layers are there and can be used for creating a Gerber stencil.
The big question is: are they included in the footprints?
You’ll have to check yourself by using the Footprint Editor.
You are right, it’s absolutely necessary to check that for each footprint (type). Some have it, some don’t.
Your remark does make me wonder… Would it be a good idea to add glue dots to all of KiCad’s footprint, or at least make some recommendation about this in the KLC? (I checked briefly, glue is apparently not mentioned in the KLC).
I guess reflow is the most common soldering technique (possibly combined with selective soldering). I’m not sure how common reflow (which needs the glue for SMT parts on the bottom) still is.
I’m not sure how critical the placement of glue dots is, and it seems a bit silly to recommend adding the glue dots for people who use reflow. But KiCads own libraries get used by all kind of people, and when the glue layers are not needed, it’s easy to ignore or disable them.
Another related topic are the custom design rules:
file:///usr/share/doc/kicad/help/en/pcbnew.html#_custom_design_rules
They do not mention glue (or gluing) or adhesive. But the custom design rules do have keywords for such things like Solderpaste_Margin_Override. It seems quite sensible to make a feature request for creating custom rules for the adhesive layers. I’m no good with these rules though. Maybe it’s already possible (and good enough) to check whether a footprint has pads aperture pads on the adhesive layer, and I also have not checked gitlab for whether a similar feature request is already present.
I don’t think it’s worth the effort. It might have been 15+ years ago.
Historically, the glue thing dates back to when SMD parts were wave-soldered in combination with leaded parts, and also to prevent tombstoning, which with modern flux is history as well.
As you say, reflow soldering is the assembly technology today
Even double-sided assembly will work without glue in a reflow environment.
I suggest adding a comment/paragraoh in the KLC (and perhaps the Manual) stating that the “Adhesive” layer is only partially supported in the standard footprint library, and that the user should check the involved footprints and modify them as needed.
Cheers.
Last week I was modifying 2 lamps at my corridor by filling it with pieces of 12V LED strip. To do it I have bought AC230 → DC12V 24W supplies. Size 2x3x10cm, price - less than $3.
Inside: single sided PCB with THT at top and glued SMD at bottom.
It have to be very mass production as got such end user price. I would be probably able for that price order only the aluminum housing of it.
Using glue looks being not history yet 
Fine with me. Let the Chinese make their own footprints with glue dots. No reason to start a project for the KiCAD library team, though.
But that’s just my opinion.
Mixing SMD with wave soldering is very unlikely to involve the smaller part sizes. It’s been a long time since I had to do this
Glue isn’t always necessary for parts on the bottom side for reflow.
Most small components, such as resistors, capacitors up to 0805, some small packages like SOT23, and even some smaller ICs will stay put with surface tension of the solder.
This is speaking from direct experience at a pretty high volume electronics manufacturers in the UK. PCBs were designed with all the heavy stuff on one side, and these went through the ovens on the second pass.
Once they worked out the limits, there were very few instances of things falling off on the lines.
Matt
Squished or squashed is fine, but squished is less formal and more friendly. Not for the thing that you squished I might add 
Small things like mice are squished, big things like elephants are squashed. Usually you can hear squishy sounds. If you can hear squashy sounds you’re too close. 
A bit more serious…
To get back to the title, I guess a “stencil” for adhesive does not exist. glue is dispensed though a nozzle that moves over the PCB. This can be either by contacting the PCB with the tip and leaving a droplet behind, or by “shooting” droplets from a small distance to the PCB. A stencil probably does not work because unlike solder paste, glue dries, and it would foul the stencil. Solder paste can also be dispensed by a nozzle (so no stencil is needed for the paste either). This used to be limited to prototypes because the process used to be too slow, but for a few years there are high speed jet printers that can print solder paste at high speeds.
Thanks, for brief solution and recommendations for a new feature. if kicad continue to provide adhesive layers in future then it will be good idea to update libraries with the adhesive layers.
one again thanks.
great, then raise a ticket to remove that option from kicad as well no need to provide those layers…
Layers needed for Gerbers to tell assembler where glue is needed?
A job for you? Some donated time?
loved your suggestion to donate time and i will.
You can start here:
Also, instead of just starting somewhere, start with introducing yourself to other library maintainers. How much do you know about those glue dots? How big do they need to be? Are there different recommended sizes for different glue brands? Once you start working on generic libraries instead of your own personal libraries it gets a lot more complex.
Also, big parts of KiCad’s libraries are generated from scripts (And those are other scripts than the footprint generators in KiCad itself. This adds more complexity, but by modifying a few scripts, lots of footprints can be modified quickly.
The video below mentions different footprint creation methods. @05:00 there is some talk about the footprint generators used internally by the KiCad project.
KiCon 2023 Generating Parts the KiCad Way
Of interest?
Dave from Eevblog published an exhibition walkaround yesterday. At 31.30 minutes see the latest solder paste printer.
That one (Starting @ 31:26) is from the “Mycronic MY700” Below is an older (from 2019) video of this machine I saw years ago, and it is what I had in mind when I wrote that comment.
It’s quite impressive, but still not faster then a simple stencil printer. Runtime is probably not important though, as long as it can keep up with the PnP machine. I guess it is mostly interesting for companies who have lots of production runs of small series, where the cost of the machine is justified by the reduction of setup time (& storage, cleaning, etc) of the stencils.
For occasional use for prototypes there are cheaper, simpler and slower printers.