PCB Varnishing

[S. Petrukhin]

Friends, I don't know anything about PCB varnishing technologies.

Now we have this process performed manually from a sprayer. I am printing 3D plugs to protect connectors, contacts, etc.

Tell me, please, about industrial systems that perform varnish coating?
I will be very happy to link to some machines.

[thm_w]

You can google it:
https://www.google.com/search?client=firefox-b-d&q=pcb+conformal+coating+machine#ip=1
https://www.chemtronics.com/the-ultimate-guide-to-conformal-coating

[otter42]

Hi,
It depends which are your EMS capabilities :
- Manual spray with manual masking (tape or objects or ...)
- Manual spray with peelable protection
- Varnish bath with peelable protection
- Robot varnishing like the exemple sended by Thm_w
Often varnishing is performed on entiere multiple boards pannel.

From my experience, nowaday when the volumes goes up it's EMS varnish with robots :
- Robot varnishing imply an initial tooling cost but is less labor cost after.
- Robot varnishing is sometime tricky to get right depending of the board design (varnish keepout area well separated from varnished area or jumbled)
- Sometimes they use two varnish compound, one is liquid the other is gel to create boundaries to avoid some spills
- It may takes sometimes to get the EMS to have a good programm and it must be check from time to time with UV Lamp but it's quite good when the EMS is good

So thinking the conformal coating/varnish at design stage is important, it makes the varnishing easier and get a better quality.

There is also a critical information, you must know which type of conformal coating you want :
- If it's too tough/hard it will reduce the lifetime of the board by adding some more stress on the parts
- If you have to perform some soldering aftewared on the board for assembly it may be better to have a reworkable varnish
- The toxidity of varnish fume can also be important

For conformal coating, in my applications I tend to prefer :
- Relatively soft varnish such as acrylic or other elastic ones
- Non toxic fume when soldered with iron (either for primary assembly or for parts alterantive testing for example)
- Easy reworkable directly with soldering iron
- ...