Project Logs

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• After Etching

  KSUdoubleE • 12/27/2021 at 14:31 • 0 comments

  The etching process went well, I'm happy with the results.  The ferric chloride I use is placed in a thick plasting zip top bag and placed in hot tap water to warm up the etchant.  I place the board in the bag and agitate every minute or so.  I checked progress after 5 minutes and the board was fully etched in about 7 minutes.

  In the past, I've always used the toner/iron method that did a good job, but there were always areas that needed touching up with a sharpie before etching.  I didn't have to do anything with this board.  The ironing part was always a pain and very touchy to get right.

  The hardest part of this process is getting the front and back lined up right.  I try to align it with two edges of the board, but that still results results in a little error.  I wil try printing a registration mark on both the front and back transparencies, and 3D print a "L" shaped jig the same thickness as the board to hold the board square and allow to align the transparencies to the jig.  The transparencies will be taped to the board or jig to hold them in place before putting the glass on top.  It might be a while before I print another board, but I'll post what I come up with and how it works.  (On these two sided boards, I try to keep the number of vias to a minimum and use chopped up through hole resistor leads in the vias as jumpers from front/back.)

• Notes on 12/22/2021 Process

  KSUdoubleE • 12/23/2021 at 05:32 • 0 comments

  Using EagleCAD to generate the Inverted PS file and using PS2PDF online converter to get PDF to print on transparency.  We want it transparent in the areas we want copper.
  

  Samsung M2830DW Laser Printer for printing on transparencies.  In the print settings, I use 100% contrast and brightness.  I also print twice and tape the two copies together in order to ensure light is fully blocked if one doesn't print 100% black in the proper areas.

  Apollo Laser Printer Transparency Film (VCG7060E) 

  Vantiyaus Photosensitive (30cmx500cm/1ftx16.5ft) PCB Photosensitive Dry Film for Circuit Production Photoresist

  AMARS Black LED Lights Strip for Decoration, DC12V 24W 5050 - Using 54 LEDs at 12V

  5 1/2" Height of UV LEDs from table

  Using a clipboard, glass, and 4 paper clamps to secure transparency to photosensitive film coated board

  Scotch TL902 Laminator for laminating the photoresistive film to both sides of the board, set on 5mm and running through 8 times, flipping sides every time

  8 minutes of UV exposure each side

  Using 1/2 teaspoon of Soda Ash (sodium carbonate) along with cup and a half of warm water to develop the photoresist.  Gentle agitation of both sides with a modified toothbrush.  Unexposed film starts coming off at the 4 minute mark and with some scrubing the process is complete at 7 minutes.  Scratching in the bare copper areas to see if film remains where it shouldn't does help.  I expose again for a few minutes if the traces aren't nice and dark.

  Results can be seen below, before Ferric Chloride etching.  I am happy with the results, all traces are there and should etch well.  For reference, the smallest traces are .016" (.4mm).  As a side note, I usually use .024" (.6mm) isolation on polygons to stay out of trouble.  With these results I could probably drop that to .016" (.4mm)  Next log will post results from etching.

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