Difference between revisions of "Developing the Board"

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Prepare the board resist developer solution using 10g of pure NaOH granules (meter using analytic balance) per liter of water (about 250ml in the small tray more than suffices). Room-ish temperature is sufficient, hot is bad (accelerates development and punchthrough, potentially just stripping all resist from the board).
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To develop the board, you will need a room-temperature bath of NaOH and latex gloves (the NaOH is somewhat caustic and shouldn't make contact with your skin). The NaOH comes in granule form and must be mixed with room-temperature water (do not use hot water). Every, 10 grams NaOH must be mixed with 1 liter of water. Using an electronic scale, measure 2.5 grams of NaOH, and using a graduated cylinder measure 250 milliliters of water, then pour the contents into a plastic tray (the solution will react with metal so do not use a metal tray). Mix the NaOH/water solution thoroughly to ensure that you board develops evenly.  
  
Holding the board in a gloved hand, immerse and gently swish/agitate it. You should promptly see green streaming/boiling/clouding off the board and the emergence of the artwork pattern. Inspect closely every 30 seconds or so - the exposed copper to be etched should be bright and shiny. Any hint of gumminess means that there is a thin film of resist still clinging to it.
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Once the solution is well mixed, use a gloved hand to gently submerge your PCB (the layers of photo resist can be damaged if the PCB isn't handled with care). The photoresist on the board should begin to "smoke" off immediately and you should keep the board moving to ensure fresh NaOH covers the board. The pattern of your artwork should become visible as the board develops.  
  
If the developer is fresh, this gumminess means that the board was underexposed. There's nothing to lose at this point by keeping going in development to see if it will clear. It will not be too very long before the caustic will begin to strip the unexposed resist as well, however.
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Check your board every 30 seconds to see the progress. When the copper layer is exposed and shiny you are almost done. Once it looks as if all the photoresist has been removed continue moving the board in the solution for 30 more seconds. Then, remove the board and run it under cold water and be sure to avoid dripping developer during the transfer process.
  
Once done, rinse both sides under fast running cold water to get the caustic off. Gently DAB dry using a paper towl. DO NOT rub: The resist isn't a delicate flower but it's not that tough either.
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To dry the board, gently DAB the surface using a paper towel. DO NOT rub the board; the resist isn't a delicate flower but it's not that tough either.
  
Pretty!
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(Some of this tutorial is based of Professor Steck's book "Analog and Digital Electronics")

Revision as of 12:00, 20 February 2019

To develop the board, you will need a room-temperature bath of NaOH and latex gloves (the NaOH is somewhat caustic and shouldn't make contact with your skin). The NaOH comes in granule form and must be mixed with room-temperature water (do not use hot water). Every, 10 grams NaOH must be mixed with 1 liter of water. Using an electronic scale, measure 2.5 grams of NaOH, and using a graduated cylinder measure 250 milliliters of water, then pour the contents into a plastic tray (the solution will react with metal so do not use a metal tray). Mix the NaOH/water solution thoroughly to ensure that you board develops evenly.

Once the solution is well mixed, use a gloved hand to gently submerge your PCB (the layers of photo resist can be damaged if the PCB isn't handled with care). The photoresist on the board should begin to "smoke" off immediately and you should keep the board moving to ensure fresh NaOH covers the board. The pattern of your artwork should become visible as the board develops.

Check your board every 30 seconds to see the progress. When the copper layer is exposed and shiny you are almost done. Once it looks as if all the photoresist has been removed continue moving the board in the solution for 30 more seconds. Then, remove the board and run it under cold water and be sure to avoid dripping developer during the transfer process.

To dry the board, gently DAB the surface using a paper towel. DO NOT rub the board; the resist isn't a delicate flower but it's not that tough either.

(Some of this tutorial is based of Professor Steck's book "Analog and Digital Electronics")