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UV Lithography For Circuit Board Creation

In this multi part series on diy circuit board manufacturing/fabrication I'm going to cover my diy, vacuum pull down UV LED exposure box.

If you are looking for a description of the entire fab process click here

UV Exposure Rig

The photos bellow are of the  uv lithography exposure box I cobbled together. It also features vacuum pull down. 

The source:

A 4.1w High luminous efficiency 365nm UV LED. Sourced from digi key mid 2016. Model LZ1-00UV00

You might note the version I bought has a dome over the emitter. They did offer a dome less version which if I recall correctly is better for providing a collimated source. I was able to produce features at 8thou with out an issue with the domed Version. The dome less was something like $30 more expensive and out of stock at the time I ordered 

The heat sink was originally from an Intel core 2 CPU. in the picture above I had trimmed it around the edges to fit into a yellow lantern.

The Frame/box

Here's a close up of the heatsink(UV LED is mounted under the metal star) and mounting bracket. 

The mounting bracket was from a ceiling light. A can style light fixture. I wasn't sure exactly how much distance I would want or need so designing it this way allowed me to reposition The source on the fly. You can probably see the wing nuts that allow for height adjustments.

I found acrylic hinges for sale on ebay and employed them for the doors.

Vacuum Pull Down

Side view reviews the vacuum pump motor and some home Depot PVC too attach it to the three plexi glass sheet thick bottom. The middle is essentially hollow between the top and the bottom of the stack.

On the inside holes were drilled through the top of the bottom plate. I then drilled a hole out one side and was able to attach some easily sourced PVC up to the pump motor. It was done quick and dirty but it worked.
Plexiglass isn't very transmissive for uv so a sheet of low iron silica glass was placed on top of the weather stripping. This allowed the vacuum to pull the transparency against the pcb to be (copper clad) 

I utilized my lifx lights set to red while working with the uv sensitive acid resist film

Clyde liked to help...(only pic I can find of them set to red)

Printed CAD design (above)

I was able to obtain features down to 8 thou with out trouble. Double sided alignment wasn't bad either but I'll keep the precise nature of how I pulled that off to my self for now

The design above(board) is very basic. It was actually the first working pcb of my own design. I hadent yet realized the benefits of a power plane and I also wasn't confident in the tools ability to produce yet. 



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