Homebrew PCBs

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/

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/





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

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


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

On Wed, 09 Jan 2013 15:47:35 +1100, you wrote:

<snip>
>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

Actually, I took some scrap MDF and made a vacuum frame.  It's just a
sealed box with an array of 1/4 inch holes in the top.  There's a hole
bored in the side which fits the vacuum cleaner inlet.  The sides are
elevated, forming a U shape.  On top of that U I sit the UV lamp
assembly (fluorescents).  I use an old enlarger timer to control
exposure (it's just a timer, no automatic exposure meter yet).

Harvey

>
>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/
>
>
>

On Wed, 9 Jan 2013 00:09:49 -0500, you wrote:

>Is PVC sheet sold at Lowes, Walmart or similar type of store?
>

I used Vinyl from a craft store (jo-ann fabrics) which has heavier
fabrics for upholstery.  Very inexpensive.  Similar stores ought to
have it, so yes, Walmart *may* have it.

Vinyl can be melted and heat sealed with an old soldering iron, you'll
need some practice to do it.  However, if you build a vacuum frame
(easy to do with lumber, you only need cross cuts and a drill), you
only need a single layer.

Harvey

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