Richard,
The bright white appearance of your lamp makes me think you actually have a "sun lamp" (that is, one that puts out a lot of near UV light) rather than an infrared lamp intended for surface heating of things. A sun lamp can cause sunburns to skin, if the exposure is long enough. As I recall, only a few minutes of exposure will cause redness (the change is not immediate) and 10 minutes exposure at a foot or two was certainly enough for a serious sunburn. The risk of sunburn for the same exposure time drops sharply as the distance to the lamp increases. The amount of skin heating was minimal compared to the amount of sunburn produced, so one would see bright-red students who had the excuse that they fell asleep under the sunlamp.
John
----- Original Message -----
From: Richard
To: Homebrew_PCBs@yahoogroups.com
Sent: Sunday, March 04, 2007 11:07 PM
Subject: Re: [Homebrew_PCBs] sensitized boards
There is no number on the lamp. It's bright white.
Richard
----- Original Message -----
From: John P. Anhalt
To: Homebrew_PCBs@yahoogroups.com
Sent: Sunday, March 04, 2007 6:02 PM
Subject: Re: [Homebrew_PCBs] sensitized boards
Thanks for the information, Richard.
That is interesting. In graduate school, we used "sun lamps" for near UV. The reactions we were studying were similar to what I understand is the basis for most positive-resist boards. I am surprised there is enough absorption of "infrared" to make the photochemical reaction go, or alternatively, enough near UV from an infrared lamp. Does the lamp have a reddish glow, or is it a brighter white? If you have the actual lamp number (which should be printed on the face of the lamp), I will check it out.
John
----- Original Message -----
From: Richard
To: Homebrew_PCBs@yahoogroups.com
Sent: Sunday, March 04, 2007 5:52 PM
Subject: Re: [Homebrew_PCBs] sensitized boards
250 watt 120 volt GE Infared Heat Lamp.
Spaced 11" from the pc board with an exposure time of 75 to 90 seconds. I generally do the 90 seconds.
I bought it at Walmart about 10 years ago and it's still going strong.
Richard
----- Original Message -----
From: John P. Anhalt
To: Homebrew_PCBs@yahoogroups.com
Sent: Sunday, March 04, 2007 9:11 AM
Subject: Re: [Homebrew_PCBs] sensitized boards
Richard,
Can you give a little more detail about the heat lamp that you use, such as brand, wattage, and identifier number on it?
Thanks.
John
----- Original Message -----
From: Richard
To: Homebrew_PCBs@yahoogroups.com
Sent: Sunday, March 04, 2007 9:40 AM
Subject: Re: [Homebrew_PCBs] sensitized boards
I use Infared Light to expose my positive sensitized boards because I can expose them in about 90 seconds using a IR heat lamp.
Richard
----- Original Message -----
From: docstein99
To: Homebrew_PCBs@yahoogroups.com
Sent: Thursday, March 01, 2007 11:28 AM
Subject: [Homebrew_PCBs] sensitized boards
I was wondering if anyone can give me some advice, looking at the
threads recently it looks like lots of people here have tried
sensitized boards.
This material appears to be the same stuff as silkscreen printers use
on silkscreens, where the exposed areas to intense light are hardened
and the unexposed areas are washed away with water.
Do any of the sensitized boards or materials react to INFRA-RED light?
I have an infra-red laser diode on a cnc machine, its not powerful
enough to cut stuff with but will smolder black foams. I was wondering
if its possible to use that to rastorize the image, but I dont know
about all the different types of sensitizer or what types of lights
they react to. I know in screen printing, they make types which react
to a 4k watt metal halide bulb, and newbie stuff that works with a 150
watt lightbulb.
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