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My new photo resist spinner

My new photo resist spinner

2010-04-17 by designer_craig

I just finished up my new photo resist spinner.

Its consists of a plywood box 15" square and 3" high with a modified
surplus computer fan mounted in the center. I found a nice 4" Nidec
fan with a metal frame and cut off the plastic blades with my band saw.
Also took off about 1/2" of the metal frame to allow the fan hub
protrude above the frame. I used some JB-weld to glue a 6" aluminum
disk to the fan hub. I mounted a push button swithch in the side and
power it with a wall-wart transformer.

I posted a picture and a short video low quality video clip at: Spin
Coater <http://picasaweb.google.com/cschaffter/DYIPCBs#>

The board is fastened to the aluminum plate with small loop of masking
tape. To coat the board I put about 1/8 tsp of the resist on the board
and spread it out with my small brush or my finger. This wets the
copper and prevents dry spots when spinning. Then I add another 1/8 tsp
in the center and turn on the spinner. I use the power button to
modulate the rpm and stop the process by eyeball.

I just started playing with the Genesis AQ3000 waterborn negative photo
resist and so far I like it. I am getting a nice even coating from the
spinner and after baking at 180 deg F the resist is nice and hard with
good adhesion. No worry about pulling off the resist with masking tape
while doing the second side. I have not etched a board yet but did a
test exposure yesterday with an old circuit negative. I think the
resist is quite sensitive, but I will know more when I get my UV box
built and receive my Stauffer 21 step test strip.

Next project will be to build the UV exposure box from a couple of 36W
nail polish curing units off ebay. UV lamp
<http://stores.ebay.com/eTech-Digital-World__W0QQ_sidZ863785197?_nkw=36w\
&submit=Search>

Craig







[Non-text portions of this message have been removed]

Re: [Homebrew_PCBs] My new photo resist spinner

2010-04-17 by Chris Maness

>
> Next project will be to build the UV exposure box from a couple of 36W
> nail polish curing units off ebay. UV lamp
> <http://stores.ebay.com/eTech-Digital-World__W0QQ_sidZ863785197?_nkw=36w\
> &submit=Search<http://stores.ebay.com/eTech-Digital-World__W0QQ_sidZ863785197?_nkw=36w%5C%0A&submit=Search>
> >
>
> Craig
>

Nice Job! For an exposure box I would recommend UV LED's. You can make a
grid for REAL cheap.

Chris KQ6UP


[Non-text portions of this message have been removed]

Re: My new photo resist spinner

2010-04-17 by James

>
> Nice Job! For an exposure box I would recommend UV LED's. You can make a
> grid for REAL cheap.
>
> Chris KQ6UP
>
>
> [Non-text portions of this message have been removed]
>


Too much work to wire up enough LEDs for even light, a UV fluorescent tube is under 10 bucks and only needs a few wires!

Re: My new photo resist spinner

2010-04-17 by bebx2000

I second the comment: "nice job". I have a couple of questions.

1. What is the rpm of the motor?
2. Is the centering or balance of the aluminum disk critical?.

Baxter


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--- In Homebrew_PCBs@yahoogroups.com, "designer_craig" <cs6061@...> wrote:
>
>
> I just finished up my new photo resist spinner.
>

Re: My new photo resist spinner

2010-04-18 by designer_craig

Baxter,
Not sure what RPM the motor is running but its fairly fast. I control the speed by modulating the power button with my finger. Guess I need to figure out how to measure it.

You want to get the aluminum disk centered as much as possible. That issue came up when I went to attach the disk to the hub. How the devel am I going to get it centered? I couldn't see the hub and I had forgotten to drill a center hole in the disk while I was cutting it out on the lathe. I mixed up the JB-Weld and coated the top of the fan hub centering the disk by eye. Then I fixed a pencil to the box with some tape as a guide with the point close to the edge of the disk. Rotating the disk and hub by hand I was able to get the disk centered quite well, it runs nice and smooth with only a hint of vibration at full speed. The blank PCB is going to unbalance everything anyway. Did a lot of boards on my old spinner years back and almost never had a board fly off. Its a good idea to spin it up before you put on the resist just to test your positioning.

Show quoted textHide quoted text
--- In Homebrew_PCBs@yahoogroups.com, "bebx2000" <bebx2000@...> wrote:
>
>
>
> I second the comment: "nice job". I have a couple of questions.
>
> 1. What is the rpm of the motor?
> 2. Is the centering or balance of the aluminum disk critical?.
>
> Baxter
>
>
> --- In Homebrew_PCBs@yahoogroups.com, "designer_craig" <cs6061@> wrote:
> >
> >
> > I just finished up my new photo resist spinner.
> >
>

Re: [Homebrew_PCBs] Re: My new photo resist spinner

2010-04-18 by Derward Myrick

Back in the ealy 1960s I worked at a Company that used a record player turntable
at 45 rpm. Worked great.

Derward Myrick KD5WWI





----- Original Message -----
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From: designer_craig
To: Homebrew_PCBs@yahoogroups.com
Sent: Saturday, April 17, 2010 7:26 PM
Subject: [Homebrew_PCBs] Re: My new photo resist spinner



Baxter,
Not sure what RPM the motor is running but its fairly fast. I control the speed by modulating the power button with my finger. Guess I need to figure out how to measure it.

You want to get the aluminum disk centered as much as possible. That issue came up when I went to attach the disk to the hub. How the devel am I going to get it centered? I couldn't see the hub and I had forgotten to drill a center hole in the disk while I was cutting it out on the lathe. I mixed up the JB-Weld and coated the top of the fan hub centering the disk by eye. Then I fixed a pencil to the box with some tape as a guide with the point close to the edge of the disk. Rotating the disk and hub by hand I was able to get the disk centered quite well, it runs nice and smooth with only a hint of vibration at full speed. The blank PCB is going to unbalance everything anyway. Did a lot of boards on my old spinner years back and almost never had a board fly off. Its a good idea to spin it up before you put on the resist just to test your positioning.

--- In Homebrew_PCBs@yahoogroups.com, "bebx2000" <bebx2000@...> wrote:




[Non-text portions of this message have been removed]

Re: My new photo resist spinner

2010-04-18 by bebx2000

Derward,

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.

If you can do this at 45 rpm, This an almost ready made solution,

http://www.allelectronics.com/make-a-store/item/DCM-351/24-VDC-GEAR-MOTOR-W/-TURNTABLE/1.html

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.

Here is another take on the fan approach,

http://www.chemistry-blog.com/2007/01/13/pimp-my-spin-coater/

Quote from the answer to a comment question:

"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."

From the photo, It doesn't appear that he is even using a a platter.

Baxter



Show quoted textHide quoted text
--- In Homebrew_PCBs@yahoogroups.com, "Derward Myrick" <wdmyrick@...> wrote:
>
>
> Back in the ealy 1960s I worked at a Company that used a record player turntable
> at 45 rpm. Worked great.
>
> Derward Myrick KD5WWI
>

Re: My new photo resist spinner

2010-04-19 by designer_craig

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

Show quoted textHide quoted text
--- In Homebrew_PCBs@yahoogroups.com, "bebx2000" <bebx2000@...> wrote:
>
>
>
> Derward,
>
> 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.
>
> If you can do this at 45 rpm, This an almost ready made solution,
>
> http://www.allelectronics.com/make-a-store/item/DCM-351/24-VDC-GEAR-MOTOR-W/-TURNTABLE/1.html
>
> 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.
>
> Here is another take on the fan approach,
>
> http://www.chemistry-blog.com/2007/01/13/pimp-my-spin-coater/
>
> Quote from the answer to a comment question:
>
> "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."
>
> From the photo, It doesn't appear that he is even using a a platter.
>
> Baxter
>
>
>
> --- In Homebrew_PCBs@yahoogroups.com, "Derward Myrick" <wdmyrick@> wrote:
> >
> >
> > Back in the ealy 1960s I worked at a Company that used a record player turntable
> > at 45 rpm. Worked great.
> >
> > Derward Myrick KD5WWI
> >
>

Re: My new photo resist spinner

2010-04-19 by James

--- In Homebrew_PCBs@yahoogroups.com, "designer_craig" <cs6061@...> wrote:
Show quoted textHide quoted text
>
> Baxter,
> Not sure what RPM the motor is running but its fairly fast. I control the speed by modulating the power button with my finger. Guess I need to figure out how to measure it.
>
>


The DC fan motors can be controlled with a simple PWM circuit, 555 driving a mosfet or transistor will do the job.

The shaded pole motors in AC powered fans will usually work on a light dimmer to vary the speed.

Either way the actual RPM is not really important, you can just experiment with speed until the results are satisfactory.

Re: My new photo resist spinner

2010-04-20 by designer_craig

You really can't use a speed controller as you need to adjust the speed as the resist spreads out and the only to do that is by eyeball.
There are just too many variables to make it automatic. The momentary on/off button works very well and it follows the KISS principal.

Craig

Show quoted textHide quoted text
--- In Homebrew_PCBs@yahoogroups.com, "James" <jamesrsweet@...> wrote:
>
>
>
> --- In Homebrew_PCBs@yahoogroups.com, "designer_craig" <cs6061@> wrote:
> >
> > Baxter,
> > Not sure what RPM the motor is running but its fairly fast. I control the speed by modulating the power button with my finger. Guess I need to figure out how to measure it.
> >
> >
>
>
> The DC fan motors can be controlled with a simple PWM circuit, 555 driving a mosfet or transistor will do the job.
>
> The shaded pole motors in AC powered fans will usually work on a light dimmer to vary the speed.
>
> Either way the actual RPM is not really important, you can just experiment with speed until the results are satisfactory.
>

Re: My new photo resist spinner

2010-04-20 by James

--- In Homebrew_PCBs@yahoogroups.com, "designer_craig" <cs6061@...> wrote:
Show quoted textHide quoted text
>
> You really can't use a speed controller as you need to adjust the speed as the resist spreads out and the only to do that is by eyeball.
> There are just too many variables to make it automatic. The momentary on/off button works very well and it follows the KISS principal.
>
> Craig


I didn't mean automatic, I just thought it might be nice to have a smooth full range control. Point taken about the simplicity though.