[Homebrew_PCBs] A different PCB etching method proposal
2013-03-02 by earlannis
Hi All,
I'm Earl Hancock, relative newcomer to this listserve, and a hobby builder of PCB's.
Built my first board in 1954 physics class, groaned through the same process in 1962 but using ortho film for my image and sunlight to expose the sensitized silkscreen and thought this is as good as it could be. I see lots of folks building UV light boxes. You might consider free sunlight for a few minutes. It works real good on sunny days.
In the 90's we were building LF cave radios to reconcile our maps and drill holes into caves (yes, up to 600 feet deep). But in 2012 we discovered a new and wonderful way to make PCBs. Nothing we invented, but combined the work of many like-minded builders. Here is how we do it.
1) Laser toner, normal settings (Brother HL2270 DW ~$80) print your circuit onto
2) Avery (or Oracal) white (any color works) Cast PVC (.003" vinyl on white paper) cut into 4x6" pieces. (very cheap, free). We have a friend who has a sign shop and his offal is plenty for our 4x6" needs. Goes through the printer like a charm.
3) Household iron set at highest setting.
4) FR4, 1/1, 1/16th inch, 4x6 inch boards (a buck apiece on eBay), stack the cleaned PCB, laser toner image on vinyl, a piece of clean white paper and iron for about 2 minutes.
5) Cool to the touch and peel vinyl and paper from PCB.
6) Use etchant (about 8oz) of 1 part Muriatic Acid (Home Depot ~$10/gal), 2 parts Hydrogen Peroxide (Walgreens ~$3/qt) at room temperature in a tray made of ½ of a gallon milk jug for about 3-4 minutes, depending on how many boards have been etched. Can be stored for 10-14 days. The solution remains clear but tinted green, allowing you to pull the board when unwanted copper is dissolved. Pour the waste liquid onto crushed limestone for Green and safe disposal. Use care with the acid. Protect back side of board with any spray paint.
7) Remove toner from board with most solvents, thinner, acetone etc.. You're done.
This whole process; from printer to drilling holes usually takes less than 40 minutes, is very cheap (less than $2 for a 2 sided board), very clean and produces excellent boards. No exotic tooling or ventilation, You may need to experiment with your wife's iron (pressure and timing) to achieve the toner transfer you desire (too much pressure/time may spread heavy deposits of toner causing shorts we use the General Print setting).
We use 20 mil traces and 20 mil spacing with never a problem. If we make a mistake (or want to practice) in melting toner onto the board wash it off and do over. Our .035 pads have holes to guide our hand held drill. Check your printer for dimensional accuracy. See photos in Earl H's album.
Others out there are doing surface mount stuff with 10 mil and getting good results.
If you want to know about the cave radios please do so off post,
Earl
I'm Earl Hancock, relative newcomer to this listserve, and a hobby builder of PCB's.
Built my first board in 1954 physics class, groaned through the same process in 1962 but using ortho film for my image and sunlight to expose the sensitized silkscreen and thought this is as good as it could be. I see lots of folks building UV light boxes. You might consider free sunlight for a few minutes. It works real good on sunny days.
In the 90's we were building LF cave radios to reconcile our maps and drill holes into caves (yes, up to 600 feet deep). But in 2012 we discovered a new and wonderful way to make PCBs. Nothing we invented, but combined the work of many like-minded builders. Here is how we do it.
1) Laser toner, normal settings (Brother HL2270 DW ~$80) print your circuit onto
2) Avery (or Oracal) white (any color works) Cast PVC (.003" vinyl on white paper) cut into 4x6" pieces. (very cheap, free). We have a friend who has a sign shop and his offal is plenty for our 4x6" needs. Goes through the printer like a charm.
3) Household iron set at highest setting.
4) FR4, 1/1, 1/16th inch, 4x6 inch boards (a buck apiece on eBay), stack the cleaned PCB, laser toner image on vinyl, a piece of clean white paper and iron for about 2 minutes.
5) Cool to the touch and peel vinyl and paper from PCB.
6) Use etchant (about 8oz) of 1 part Muriatic Acid (Home Depot ~$10/gal), 2 parts Hydrogen Peroxide (Walgreens ~$3/qt) at room temperature in a tray made of ½ of a gallon milk jug for about 3-4 minutes, depending on how many boards have been etched. Can be stored for 10-14 days. The solution remains clear but tinted green, allowing you to pull the board when unwanted copper is dissolved. Pour the waste liquid onto crushed limestone for Green and safe disposal. Use care with the acid. Protect back side of board with any spray paint.
7) Remove toner from board with most solvents, thinner, acetone etc.. You're done.
This whole process; from printer to drilling holes usually takes less than 40 minutes, is very cheap (less than $2 for a 2 sided board), very clean and produces excellent boards. No exotic tooling or ventilation, You may need to experiment with your wife's iron (pressure and timing) to achieve the toner transfer you desire (too much pressure/time may spread heavy deposits of toner causing shorts we use the General Print setting).
We use 20 mil traces and 20 mil spacing with never a problem. If we make a mistake (or want to practice) in melting toner onto the board wash it off and do over. Our .035 pads have holes to guide our hand held drill. Check your printer for dimensional accuracy. See photos in Earl H's album.
Others out there are doing surface mount stuff with 10 mil and getting good results.
If you want to know about the cave radios please do so off post,
Earl