I am using FR4 with a solder cover as substrate and I want to bond Cured or uncured PDMS to it. What are the possible methods I can use. to bond them ?
It depends on what the role of the PDMS is in your application.
You can coat with uncured PDMS and then allow the PDMS to cure slowly to produce a thin film. This works well if it is to be used as a protective/sealing layer.
Otherwise if you have a block of PDMS, first make sure you do not over-cure (it will become brittle). Then, if possible, perform UV-Ozone treatment before attaching it to the FR4/soldermask.
Jules
Hello,
To expand on Dr Hammond's excellent suggestions, here are some thoughts from my experience.
1. Make sure you clean the FR4 boards throughly in solvent.
2. Using a silane surface treatment may be helpful here.
3. In addition to using uncured PDMS as a glue, if your application allows, you might also spin/apply a thin layer of PDMS to the surface and allow it to cure. You can then perform a PDMS/PDMS bond using oxygen plasma, etc.
4. In the past, while fabricating PCBs, through-holes and grooves were added to the design, allowing PDMS to flow through the board to the backside to help anchor the polymer to the surface.
Hi,
Though uncured PDMS is one of the best options, you can resort to other adhesives for this purpose. If possible, try to use SU-8, a negative photoresist for this purpose.
You can also try to activate the surface by silane treatments or by oxygen plasma exposure. That might also help.
Best,
Jose