Interesting links.
The thicknesss of the water based Aq3000 I am currently spinning mostly depends on the speed and viscosity since the evaporation is fairly slow. The AQ3000RC I have is compounded for roller coating and from what I have seen so far he viscosity is just a little higher than optimal. I had to add a little water to help out with some larger boards.
Another factor is the aspect ratio of the board. Boards that are 4- 5" sq or less are fairly easy to get a nice even coat. On larger boards the chance of edge streaking increases and the edges are always going to have a thinner film thickness than the center. Yesterday I did a couple of what I belive were 3x6 inch boards for Volkan. After a couple of attempts I got a good coat on both sides.
We tested these on his UV laser writer, the resoluiton blew me away its just awesome with crisp edges and very fine line difinitions.
IMOP 45RPM is not going to be enough to spin a board. I haven't measured my RPM yet but I figured out how to do it and will post the results. Based on a sampeling of fan RPM's from the Nicec web site the rpm range from 4000 to 10000. When spinning you can see the resist thinning out in the center as the color changes from blue to copper color as the film begins to thin. I use my on/off button to modulate the rpm and I have had it up to the fan's max rpm.
Craig
--- In Homebrew_PCBs@yahoogroups.com, "bebx2000" <bebx2000@...> wrote:
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>
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> Derward,
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> I investigated spin coating a bit further,
>
> http://en.wikipedia.org/wiki/Spin_coating
> http://www.clean.cise.columbia.edu/process/spintheory.pdf%20%20
> http://www.ece.gatech.edu/research/labs/vc/packaging/theory/spin_theory.html
>
> It seems as though 1200 -4800 rpm is the approximate speed of rotation.
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> If you can do this at 45 rpm, This an almost ready made solution,
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> http://www.allelectronics.com/make-a-store/item/DCM-351/24-VDC-GEAR-MOTOR-W/-TURNTABLE/1.html
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> However, my reading of the above references suggests that the thickness of the coating is proportional to the speed and viscosity. I may try the allelectronics motor, but I like the fan solution of designer_craig.
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> Here is another take on the fan approach,
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> http://www.chemistry-blog.com/2007/01/13/pimp-my-spin-coater/
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> Quote from the answer to a comment question:
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> "I use velcro to hold the samples down. The pc fan is an Antec tricolor pc fan. It takes DC Power, we can vary it from 0-12V depending what speed is needed. The fan was able to spin from 0 rpm up to around 2500 rpm."
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> From the photo, It doesn't appear that he is even using a a platter.
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> Baxter
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> --- In Homebrew_PCBs@yahoogroups.com, "Derward Myrick" <wdmyrick@> wrote:
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> >
> > Back in the ealy 1960s I worked at a Company that used a record player turntable
> > at 45 rpm. Worked great.
> >
> > Derward Myrick KD5WWI
> >
>