Homebrew PCBs

It is sold at tap plastics

Sent from my iPhone

On Jan 8, 2013, at 9:09 PM, "Jeff Heiss" <jeff.heiss@...> wrote:

> Is PVC sheet sold at Lowes, Walmart or similar type of store?
> 
> Jeff
> 
> _____ 
> 
> From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
> On Behalf Of Robin Whittle
> Sent: Tuesday, January 08, 2013 11:48 PM
> To: Homebrew_PCBs@yahoogroups.com
> Cc: Harvey White
> Subject: [Homebrew_PCBs] Vacuum-seal bags, DIY PVC bag vacuum "frames" &
> 500W halogen light sources
> 
> A video http://www.youtube.com/watch?v=8WJn5YFANxU demonstrates exposing
> the Riston-like Puretch negative photoresist film:
> 
> http://www.capefearpress.com/puretchpcb.html
> 
> using a vacuum bag for sealing clothes or food. This has a zip lock and
> a valve for removing the air with a vacuum cleaner and retaining the
> vacuum after the vacuum cleaner hose is removed.
> 
> Exposure is via a 500 watt halogen incandescent lamp from a hardware
> store. I use a lamp such as this at a closer distance, with the lamp
> pointing downwards (without its glass cover, to improve airflow cleaning
> of the lamp). I use the glass cover to press the phototool onto the
> PCB, which is supported by foam. However, it would be better to use
> vacuum and a flexible top cover in place of the inflexible glass, since
> the flexible cover and air pressure would press the phototool right up
> to the PCB, even if the PCB was not flat, with less effects due to dust
> between the phototool and the PCB, and with little or no problems due to
> dust between the phototool and the flexible cover.
> 
> This vacuum-sealed bag approach looks inexpensive and effective.
> However, I think it is important to blow air on the PCB so it doesn't
> heat up too much. Temperature changes could cause the phototool to
> expand at a different rate to the PCB, leading to loss of resolution.
> 
> As Harvey White wrote ("UV nail lamps - . . .":
> 
> http://tech.groups.yahoo.com/group/Homebrew_PCBs/message/31264
> 
> it would also be possible to make a custom-size bag using PVC sheet from
> a furniture store. Vacuum could come via a small tube inserted into one
> corner of the bag, with the other end connected to a vacuum cleaner or a
> pump from a desolderer. There's no need for a valve - just run the
> vacuum cleaner while the exposure is taking place.
> 
> Since the ~0.5mm PVC is cheap and the bags can be made easily with
> scissors and adhesive tape etc. in sizes which are most suitable for PCB
> work, I think this may be a good alternative to a vacuum frame with a
> flexible top and a solid or foam-and-solid base or to any vacuum frame
> with a rigid (glass or acrylic) top.
> 
> The PVC would be less likely to wrinkle or become scratched during use
> than the polyethylene of the vacuum-seal bags. The PVC is so cheap that
> if it does become scratched, then it will be easy and inexpensive to
> make another bag.
> 
> I will write to the list when I try this - which could be a few months
> or more.
> 
> - Robin http://www.firstpr.com.au/pcb-diy/
> 
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> 
> 


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