I have prepared a solution of PDMS, ethyl acetate and ZnO nanoparticles for coating on a copper substrate. I used 10:1 mix of PDMS and its curing agent. The solution is spin-coated on a copper substrate and needs to be dry out completely. I used heat treatment for drying the coating at 100-120* C, but PDMS is still sticky. Can anyone suggest me the proper method to dry out the layer? I need to sputter Copper electrode, once the PDMS layer dries out. Please help.
Hi Rohit,
Sylgard PDMS 184 if mixed in 10:1 ratio should should completely polymerize within 1 hr at 100 C. However if PDMS is still sticky it means that probably some of the extra components that you are adding is delaying/preventing its polymerization. You can try increasing the amount of corsslinker and may be use a different ratio ... like 5:1(10:2) and try out.
I am using Sylgard 184 pdms. I tried with 10:1& 2:1 ratio but I'm facing similar problem. May be Debashish is correct that other chemicals delaying the process of polymerization. I never tried degasing before. Will try to follow Andrew's instructions too.
Sulfur prevents PDMS from curing. But thin layers of PDMS can have problems curing even in the absence of sulfur. I suggest using the thickest layer of PDMS that is useful to you.
Andrew H Cannon, Ph.D.
Research Micro Stamps
researchmicrostamps.com
519 College Ave | Suite 33282
Clemson SC 29633 USA
Hi Rohit
I am also facing the same issue. I have coated PDMS on Cooper surface and followed the same step as you did. But still it results in sticky surfaces. How did you resolve this issue.
Thanks and Regards
PDMS and curing agent ratio is very important while coating pdms thin films. Normally, 10:1 ratio is suitable for it. Once ratio is prepared, one need to degas it and then coat on the substrate. Once coating done, heat treatment need to be done. On 100-120 degree C films heated for approx. 1 - 2 hrs. This may solve the problem.
Thanks for your kind reply. Actually I have followed the same step except the heat treatment was done at 100 degC for 1hr. So I will extend the duration as you suggested.
How to determine if coating is correct. At the end of baking stage, should it be slippery (like polished surface) or slightly sticky.
P.S.- I am trying to coat 30um PDMS over copper coated PCB
Thanks and regars
Hi All
Thanks for your questions and answers. I met the same issue for curing the PMDS coating layer on membrane surface at 100oC. It's still a tacky surface after 1 hour curing. Is possible to reduce the curing time to a couple mins by inreasing the temperature (say to 120-150oC) plus blowing?
Chao Ji
UNSW PostDoc
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