Homebrew PCBs

----- Original Message ----- 
From: "Leon Heller" <leon.heller@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Friday, September 15, 2006 7:40 AM
Subject: Re: [Homebrew_PCBs] Re: UV exposure boxes


> ----- Original Message ----- 
> From: "Andrew" <andrewm1973@...>
> To: <Homebrew_PCBs@yahoogroups.com>
> Sent: Friday, September 15, 2006 4:22 AM
> Subject: [Homebrew_PCBs] Re: UV exposure boxes
>
>
>>> > Me wrote:
>>> >The kalex box has light and dark patches.
>>
>>> Tubes are probably spaced too far apart.
>>
>> My guess too.
>>
>>> I started with this;
>>> http://www.pbase.com/eldata/image/52324065
>>> Then went to this to ensure that would never
>>> be a problem;
>>> http://www.pbase.com/eldata/image/52321530
>>
>> Now that would have to be pretty even
>> illumination
>>
>>> I'm not a fan of UV tubes as you can see.
>>> In fact the only UV tube here is in a 28
>>> year old EPROM eraser.
>>
>> AFAIK there are 3 common types of UV tube.
>>
>> The generic part numbers for these start
>> GT, BL and BB.  That is for
>>
>> GT - Germicidal  = Nasty UV
>> BL - Black light = Bug zappers
>> BB - Black blue  = Disco lights
>>
>> The two second sort (BL and BB) are abouts
>> the peak sensitivity of UV resist (at least
>> kinsten brand)
>>
>> With some playing I did with them the
>> exposure times with normal white fluros
>> was significantly longer.  Theory I have
>> read says that a shorter exposure leads
>> to better line deffinition.  This may be
>> bunk - I don't know.  The white tubes
>> doubling as a light box is a good idea
>> if you do go that way.
>>
>> I woudl imagine the number of tubes
>> Derek has would lead to pretty short
>> exposures anyways.
>>
>> BTW - the GT tubes are no good for PCB
>> exposure either.  They are too short a
>> wavelength. They are only good for
>> EPROMS, killing bacteria, making ozone
>> and going blind.
>>
>> BL and BB tubes can obviously be looked
>> at with no ill effects apart from those
>> you would get from drinking to much while
>> sitting on the patio or at the disco.
>
> The germicidal tubes work fine for me.

Sorry, they are not GT (I used to use them for EPROMs) - they look like 
white fluorescent tubes.

Leon