Homebrew PCBs

As I wrote, I know it works but the question is why.

Bertho

 

From:  Andrew Volk   Sent: Sunday, April 07, 2013 02:08



Spin coating is uniform enough that it is also used in the manufacturing of
silicon wafers for integrated circuits. You want to talk about holding fine
lines? Try 50 nanometers. That is 500 Angstroms, 0.000002 inches.
Spinning works.

From: Homebrew_PCBs@yahoogroups.com <mailto:Homebrew_PCBs%40yahoogroups.com>
[mailto:Homebrew_PCBs@yahoogroups.com
<mailto:Homebrew_PCBs%40yahoogroups.com> ]
On Behalf Of Boman33
Sent: Saturday, April 06, 2013 10:48 PM
To: Homebrew_PCBs@yahoogroups.com <mailto:Homebrew_PCBs%40yahoogroups.com> 
Subject: RE: [Homebrew_PCBs] Re: Seno 100 photo resist applicator

I know spin coating has been used commercially but it always bothered me
since I do not understand how it can be a uniform coating. Basically there
is zero centrifugal force in the center and lots at the edges. How can that
create a uniform coating?

Decades ago I used to coat PCBs by SLOWLY withdrawing them from a skinny
rectangular tank which left a uniform coating except the bottom edge.
Placing the PCB still vertically on a tissue paper drained off the excess at
the edge.

Bertho

From: James Sent: Sunday, April 07, 2013 00:15

On 07/04/13 15:58, Todd F. Carney / K7TFC wrote:
> Ben,
>
> I think he was referring to the capacity of the spin machine he showed in
> the photos. I used to use spin coating, and there's no reason it can't be
> bigger.

How fast does it have to spin? The velocity of the outside edge of the 
board would be getting quite high I imagine as you increased the board 
size.






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