Prototyping PCB using LCD
Proximity Photomask Stereo-lithography
Just to share results of a project into using LCD display to expose photo sensitive coated PCB and also coating PCB's with 3D printer resin as a photo etch resist in the same way SLA 3D printers work.
UV back-light we reviewed our existing UV exposure box that uses UV tubes and also making our own UV Led panel.
There are some good disucssion related to this topic on build your own sla
Bungard PCB UV sensitive characteristics: 350-450 nm
LCD Panel UV filter characteristics: 405-410 nm. Some specs mention 410 and higher are not filtered. A high resolution and large working area is possible with the 4K TN panels. This means, theoretically that with a resolution of 3840 × 2160 on a a 24" panel, then that is 183.58 PPI or 183.58 per 2.54 centimeter. Then each pixel is 25.4 mm / 183.58 = 0.138 microns.
UV LightBox characteristics: UV florescent tubes typically 350 - 400nm
3D Printer Resin UV curing characteristic:UV up to 440nm. The higher up in the UV spectrum the slower curing time, but at 410nm it's possible to cure a 1mm blob of resin in 8 seconds.
UV LED characteristics:395 - 410nm . You can see in the diagram there is a very narrow peak wavelength. If LCD is really 405-410nm then power of the LED's are being filtered out.
Blue LED's: normally around 465-468nm
Violet 10W LED: 410-420 nm
Light Box Ideas
I liked the idea of having both UV and RED leds in the lightbox as it allows you to align the PCB to the image using the red LED's before exposing with UV
Some main challenges:
The UV Lightbox wavelength is being filtered by the LCD display, so no curing of resin and does not expose UV sensitive PCB material
the blue LED's seem to cure the UV resin but no expose the Burgard UV sensitive PCB
the main challenge is finding a screen that hasn't UVA filters so to enable the UV curing / exposure. Bangaard boards peak wavelength I believe is around 380nm and UV resins are also in the same 400nm area but vary.
I see fellow hackers are reviewing and testing screens such as 2048x1536 Resolution on a 9.5" " and 4K screens such as some of these:
(Note: we have no details whether these have been checked regarding uva filtering and therefore may not really be suitable:
http://www.pollin.de/shop/dt/MTQ5ODc4OTk-/Bauelemente_Bauteile/Aktive_Bauelemente/Displays/20_3_cm_8_Display_Set_mit_Touchscreen_LS_8T_HDMI_DVI_VGA_CVBS.html (Note: this one we tested and has very aggressive UVA filters so is not suitable OTB)
Control boards for retina displays:
Example of using LCD as photo mask:
Example of using SLA resin
LCD display source: http://www.ebay.de/itm/BN-9-7-RETINA-DISPLAY-SCREEN-APPLE-iPAD-3-4-LIKE-LG-PHILIPS-LP097QX1-SP-A1-/161975309619?hash=item25b67b1533:g:v1sAAOSw~OVWvKli
Tool for Creating TFT Panels: https://nextion.itead.cc/resources/download/nextion-editor/