Could anyone explain what may be happening with my etching. It seems like maybe the unexposed photoresist is simply not washing away.
Here are some details of my process.
I'm using single sided boards. I scrub the copper clad board with a scotch bite pad and dish soap. I thoroughly rinse and dry with kimwipes. I then store them face down on a kimwipe in my work area to prevent dust from settling on the surface.
In a dark room (using a bug light), I apply negative resist film to the copper board and slowly peal the layer back. I typically can get no air bubbles if I take my time. I then laminate the resist on the board with an amazon branded laminator. I'll pass it through 3 times at full heat.
I then expose the board for 7 minutes with the circuit layout I've exported from eagle. I use two laser jet transparency printouts doubled up. I ensure that my image is as clean as possible, if not I print another set. I check the exposed board under the bug light if I see blurriness I remove the resist and start over.
If the exposure looks good I peel off the protective film on the exposed resist and submerge the board in a solution of hot tap water and about a tablespoon of sodium carbonate. This causes the unexposed resist to turn milky. Using an acid brush I gently wipe the board until I can no longer see the milky film on the board. This usually takes only a couple of minutes, but seems to be where my problem is. Smaller traces, thermal ground plane holes, etc are very hard to see under the bug light and don't seem to like to give up the emulsion. I have tried letting the board sit in the sodium carbonate bath longer and also being more aggressive with the brush in these ares but neither have helped.
I rinse the board in tap water after the sodium carbonate bath. If I see obvious signs of the emulsion not being removed then I just remove the resist and start over, in most cases it's hard to tell though. I then submerge the board in ferric chloride, heated enough to slightly steam, and use an acid brush to move the solution over the board. This usually only takes about 8-10 minutes. I rinse in tap water after and remove the exposed resist using about a tablespoon of sodium hydroxide in a Pyrex dish of water.
In most places I get a great etch, but some places it's like the emulsion would not come off. I was using 10mil traces and 10 mil clearance, but the clearance was not etching totally. It was inconsistent though. In the same place on one board where there was no etch, the next board would etch there but not somewhere else.
I eventually changed my clearance to 20mil and got a good etch but I'd like to get 10 mil to work if possible.
Here are some details of my process.
I'm using single sided boards. I scrub the copper clad board with a scotch bite pad and dish soap. I thoroughly rinse and dry with kimwipes. I then store them face down on a kimwipe in my work area to prevent dust from settling on the surface.
In a dark room (using a bug light), I apply negative resist film to the copper board and slowly peal the layer back. I typically can get no air bubbles if I take my time. I then laminate the resist on the board with an amazon branded laminator. I'll pass it through 3 times at full heat.
I then expose the board for 7 minutes with the circuit layout I've exported from eagle. I use two laser jet transparency printouts doubled up. I ensure that my image is as clean as possible, if not I print another set. I check the exposed board under the bug light if I see blurriness I remove the resist and start over.
If the exposure looks good I peel off the protective film on the exposed resist and submerge the board in a solution of hot tap water and about a tablespoon of sodium carbonate. This causes the unexposed resist to turn milky. Using an acid brush I gently wipe the board until I can no longer see the milky film on the board. This usually takes only a couple of minutes, but seems to be where my problem is. Smaller traces, thermal ground plane holes, etc are very hard to see under the bug light and don't seem to like to give up the emulsion. I have tried letting the board sit in the sodium carbonate bath longer and also being more aggressive with the brush in these ares but neither have helped.
I rinse the board in tap water after the sodium carbonate bath. If I see obvious signs of the emulsion not being removed then I just remove the resist and start over, in most cases it's hard to tell though. I then submerge the board in ferric chloride, heated enough to slightly steam, and use an acid brush to move the solution over the board. This usually only takes about 8-10 minutes. I rinse in tap water after and remove the exposed resist using about a tablespoon of sodium hydroxide in a Pyrex dish of water.
In most places I get a great etch, but some places it's like the emulsion would not come off. I was using 10mil traces and 10 mil clearance, but the clearance was not etching totally. It was inconsistent though. In the same place on one board where there was no etch, the next board would etch there but not somewhere else.
I eventually changed my clearance to 20mil and got a good etch but I'd like to get 10 mil to work if possible.
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