Do you mean silk screen printing? It was used by English Electric, Kidsgrove, when I was a student apprentice there in the early 1960s. I worked in the PCB department for a couple of weeks. It was OK for the boards they used then, but it wouldn't be suitable these days.
Hello Bruce and Leon
'
Have you tried any spray-on developer?
'
Have you found a place to get this in the USA? [EMAIL="'@Bruce"]'@Bruce[/EMAIL]
'
I have a few(more like several/OK a dozen)~1"sq. pcbs that I have botched the developer-film in my testing.The boards are fine,Just no developer film on them.
'
It would be nice to recycle these pcbs.(apply new photo film)
'
I'm also re-thinking the toner transfer method.So all hope is not lost with the botched pcbs.
I transfered a plan paper toner transfer to a copper pcb with really good results.(special heater set-up)
'
I'm just looking for something convenient that I can make at home for a one of pcb.
I have a few(more like several/OK a dozen)~1"sq. pcbs that I have botched the developer-film in my testing.The boards are fine,Just no developer film on them.
'
It would be nice to recycle these pcbs.(apply new photo film)
I was just discussing the same subject earlier today
And in answer to your question, no, I have not found anyone that sells Positiv 20 in the USA.
I'm just looking for something convenient that I can make at home for a one of pcb.
Walt, I am getting very close to producing very nice boards with my exposure box. By the end of today, I should have it whooped. I would suggest building one of these exposure box/cylinders, and then I will send you a complimentary exposure plate and exposure plate holder (with the exception of a few parts that could be purchased locally).
We had some spray-on resist available some years ago that worked quite well, and I made a few boards using it. However, the formulation was changed (something to do with health and safety, I think) and the new stuff didn't work. I complained to someone from the company at a trade show, and he admitted that there was a problem.
A few members of the Homebrew PCB group buy dry-film resist and coat their own boards. It's only available from suppliers in large rolls, but some people resell smaller amounts to other hobbyists. Paradoxically, the best way to apply it at home with simple equipment is under water.
In an attempt to gain a little more control and not push the exposure box to it's limit, I exchanged the previously installed 40 watt bulbs for 25 watt bulbs. After (4) tests, with exposure times ranging from 1 minute to 5 minutes, I have come to the conclusion that the 25 watt bulbs are incompatable with the exposure box system. I would assume that the 25 watt bulbs are having a very difficult time of properly exposing the board while using vellum as a positive medium. I have decided to return to the use of 40 watt bulbs. Considering previous tests with the 40 watt bulbs, I will have to pay very close attention to the time clock, because exposures will now be under a minute. I now need a new clock that displays seconds. I am half-tempted to reappropriate the timer from my larger exposure box.
@Leon and Bruce
I'm glad to see that I'm not the only one that can't find the spray on developer.
'
'
Test point
'
I think knowing what the film is made of would help to determine how to expose it.
I think I know the smell of the film after removing the protective cover layer.I think its vinyl acetate.This is used to make Latex.
Latex is very biodegradable by light sources.(UV,IR.temp.,etc.)
'
Just some added info to add/consider in the test realm.(I like details)
'
@Bruce
I'm glad to see your dialing in on the process.I still see some variables that are temperature related issues that need to be addressed.
I could be wrong.But if the film is Latex based then temperature will play a huge roll in the process.
I plan on looking at the exposer board temps in my next test run.And the room temps as well.
'
I'll report back with the Data I gather from these tests.
I am looking for some ideas pertaining to temperature control of a corrosive chemical that I am using in a set of experiments. My experiments consist of exposing and developing Premier PCBs from Philmore DATAK, and the corrosive chemical is a mixture of sodium hydroxide and water.
After many experiments, I have come to realize that the temperature of the developer (sodium hydroxide and water) is of vital importance. If the developer is too cold, the board will not develop, and if the temperature is too warm, it dissolves too much photo-resist off of the PCB.
I am currently using an old Mr. Coffee to heat the developer, but I need better temperature control. More specifically, I need a method of monitoring the temperature of the developer. I believe I can hack the coffee maker for on/off time periods, but what would be a good method for monitoring the temperature of this corrosive chemical and applying it to the on/off control of the coffee heater?
At this point, let me remind you that Philmore DATAK recommends a developer temperature between 100 and 110 degrees fahrenheit for their Premier boards, which is the type of board that I am currently testing.
Eventually I will create a final and more elegant solution to this problem in association with the coffee maker, but for now, I want to do some more testing with exposures, so this is my proposed temporary solution and procedure. On second thought, let me first tell you that I am using an oven-safe bowl in combination with the coffee maker to heat the developer. Anyhow, as you can imagine, it takes a little time to heat the coffee maker, the bowl, and the developer. Using a standard thermometer, like the one used to take a persons temperature, turn the coffee maker on and drive the temperature up. The thermometer that I have has a maximum temperature of 106 degrees fahrenheit. There is no way that I will be able to stop this drive in temperature right at the thermometer maximum, so I will simply exceed the maximum. I will then keep taking temperatures of the developer until the temperature reading registers approximately 105.9 degrees fahrenheit. At this point I will take my previously exposed PCB and set it in the developer. Considering that it takes a while to heat the solution up, it will also take a while to cool down, which should permit me with ample time to develop the board. It is not an elegant solution, but it should work until I get a permanent solution.
I performed a similar procedure as stated in my previous post, except that I drove the temperature up to 102 degrees fahrenheit and then shut the coffee maker off because I knew the temperature would continue to rise. I then got a little impatient, because the thermometer remained off-scale, and I figured that it must be around 110 degrees fahrenheit. Needless to say that I ruined another sample board. I am not a person easily swayed by my own stupidity, so I immediately exposed another board and tested the developer temperature. The temperature reading was now at 104 degrees fahrenheit. Instead of heating another batch of developer, I plopped the newly exposed board into the previously used developer. Within approximately a minute to a minute and a half, I removed the best looking board that I have acquired from these experiments. I can't say that it is 100% perfect, but I would definitely give it a 95%. It's looking good.
I was not going to post this information until the experiments were complete, but just in case someone is reading this and following along, here is the current mixture of my developer used for Premier Pre-Sensitized Positive Acting Printed Circuit Boards from Philmore DATAK:
12 fluid ounces of tap water
3 grams of Rooto Crystals of Household 100% Lye Drain Opener (available at ace hardware)(caustic soda/sodium hydroxide)
Additionally, the current exposure was made with my exposure box/cylinder described at http://www.novelsolutionsonline.com/exposurebox.htm. It is a double-sided exposure and the board was exposed for a period of one minute with a 40 watt bulb on each side of the board.
I am starting to get excited again
Bruce
EDIT: It is worth mentioning, that if you are using these boards and attempting an exposure with a different exposure setup, you may need to alter your bulb wattage, exposure time, etc... The exposure box/cylinder that I was using is constructed from tin and the bulbs are contained within a highly reflective housing.
This thread is becoming more like a journal with each and every post.
I can now unequivocally state that the temperature of the developer is one of the primary factors in developing a nice board using the materials as stated in previous posts. I can clearly see an improvement and the difference after the developing process is complete. Developing times are now pretty consistent, and the photo-resist looks more intact than previous experiments.
I just did another exposure, but this time I increased the exposure time to 1 1/2 minutes with the hope that the photo-resist would dissolve more easily and leave less haze. I am happy to say that this exposure looks a little better than the last one. I am certain that the exposure time is not perfect just yet. So now I wonder whether to increase the exposure time just a little more or should I decrease it? I think I will bump it up another 15 seconds just to see the results. Since I am at this stage of the game, I could probably use the test procedure that Leon mentioned earlier in this thread, but I think I will continue with the way that I have been doing it so far, because at this point, I think I have a pretty good routine going and I believe it will only be just a few more exposures until I get it to the 100% mark.
I think that not using proper transparencies might be causing some of your problems. With vellum the exposure becomes very critical, and getting an optimum time might even be impossible. I get a lot of latitude with my UV process.
To be perfectly honest, I would be happy walking into a print shop and having them make a positive for me, but the print shops in my area don't carry the proper equipment anymore.
Additionally, I would use transparencies, but I currently get a lot of streaking, therefore I am using vellum to get a better quality positive.
I can be a very picky person, and it definitely holds true in this instance. I am sure a lot of people would have been more than pleased with some of my results so far, but like I said, I am striving for perfection.
Just wait until I post some pictures before giving vellum a bad reputation.
I could probably get perfect transparencies from my LaserJet 6L, but that would require taking it apart and cleaning it, which is a pain. However, the printer has never been the same after dropping a hot cigarette down the paper tray area. OOOPPPSSSS
I do not have any pictures just yet. My brother is the one with all the nice camera equipment. When I get the process perfect, I will run a sample to his house and use his nice Canon with telephoto zoom. The sample board is about the size of a quarter and it has a few areas of pretty fine detail. So when I take the pics, I will take them next to a quarter for size comparison.
However, here is the design that I am using for front and back.
Bruce---
'
Looking forward to the PICs of the sample PCB's
'
It sounds like you have " NAILED-IT "...!!!
'
I'd like to recommend a test with a real circuit and a copper poor before (you) call this a perfect set-up.I have found that things really change with a copper poor.
'
Of coarse this might be a little to early in the design state!
'
I'm just excited about being able to make a nice "one of PCB" at home!
'
My test results are running right close to yours,So I think we (Your) very close to perfection.
'
I'll be the first to buy your exposure set-up when its ready.
For my next sample, I am going to duplicate my business card in copper and tin coat it
I'm just excited about being able to make a nice "one of PCB" at home!
I won't get excited until I get the next PCB driller constructed and programmed, but everything is looking quite promising. The PCB cutter works like a dream and I just love that machine And now, as you put it, I believe I have the exposure box process pretty well nailed. It won't be long and I should have the ideal setup for prototyping at home, but I really need to get better organized, as I learned through this experimentation. I would imagine that once I am organized, I should be able to fab a difficult board in about an hour. I just wish I had not drilled those ventilation holes in my nice exposure box, because I really did not need them with 40 watt bulbs and exposure times under 5 minutes, and now they are just a source of unwanted light. It looks like I will have to get two new tins.
I'll be the first to buy your exposure set-up when its ready.
I do not sell the entire expose box assemblies due to laws concerning underwriting. I only sell the hardware kits and exposure plate assemblies for the exposure box. In a previous post, I suggested that you make one of these, and said that I would give you a complimentary exposure plate assembly with the exception of a few minor parts. I still suggest the same. It is a very nice little unit for doing boards 3 X 4 or less.
With the boards now being processed with the developer being in the temperature range as specified by the board manufacturer, the results are now much more consistent, however I am still toying with the process just a little. All of the traces widths are turning out nice, including the 0.004", but the fine print of the web address on the sample has been giving me some problems with clarity. I am still working on that problem and I may have to resort to transparancies as Leon stated, but I am still attempting to accomplish a crystal clear photograghic image with vellum.
Additionally, after making my awesome PCB cutter, I got so excited to start making samples that I got a little sloppy when making my exposure plate and provided just a little too much clearance for the board to move around. With this additional, unnecessary clearance, if the positive image of vellum is not perfectly aligned with the board, it produces small unwanted wire traces along the unaligned edges of the board. So it is needless to say that I need to make a more accurate exposure plate for myself, just as if I was creating one for a customer. I want this sample to sparkle with quality.
And as a side note, just in case nobody caught the edit in the "un-perfect process" above, I have bumped up the exposure time from 1 minute and 45 seconds to 2 minutes.
I have made a new exposure plate for making the samples and this exposure plate has much tighter tolerances than the previous one. With these tighter tolerances, I should be able to produce much better looking samples. I will return to the experimentation process sometime Sunday evening.
I have recently learned that I was apparently no where near the perfect process yet and I am still learning the intricacies pertaining to the use of my exposure box in combination with the Philmore DATAK Premier Series Presensitized Positive Acting PCBs. Considering what I have learned during this experimentation process, I cannot over-emphasize the importance of the developer temperature and I have established the fact that all of my experiments prior to having the developer at a proper temperature were utterly useless.
After doing some more research and considering that I am now developing at a controlled temperature, I decided to bump the bulb wattages back upto 60 watts and try these bulbs again at an exposure time of 2 minutes. With the bulbs at 60 watts, exposing the boards for 2 minutes, and having the developer at a temperature of 104 fahrenheit, I have now produced the best looking developed board so far. I am now further convinced that I am still nowhere near the perfect process yet and that it is still a learning process.
To obtain even more control, with the intent to eliminate potential error or deviation from the process, I have decided to set aside a specific area for PCB processing. This area will not have any access to sunlight or stray rays from fluorescent lighting, and a safelight will be provided by a yellow 25 watt bug light as suggested by the board manufacturer.
Bruce--
'
I have run some more tests with a highly controlled environment.Much like the one you have mentioned above.
'
I'm still seeing an unexplained variable.(Inconsistencies from one board to another)
'
I think this variable is the age of the film on the DataK board.
'
Have you noticed anything like this?
'
Not sure how to read the date code on the DataK boards...If there is a date code.
You have to imagine that my controlled environment is constantly changing
Additionally, removing the inconsistencies is the main reason behind testing
The largest inconsistencies that I have noticed has been due to developer temperature and mixture. Now that I am controlling the temperature, I am having much better consistency. However, I am getting ready to change the mixture of the developer again, because I believe I have the "exposure" process pretty well nailed (which may still need a little altering here and there).
I do not know how you are performing your tests, but my main goal right now is trying to achieve the best exposure. I would imagine that I have developed at least 40 - 60 exposure tests, but I have only etched about four samples. You must keep in mind that you will never get a good etching unless your exposure and photoresist are in good shape. Before etching any boards, try to achieve a board that has a crystal clear image of photo-resist without any remaining haze on the board. Above all else, keep in mind that it is a photographic process and that you are looking for the best image possible with the photo-resist, and that the etching is a direct by-product of this image.
If you refer to my post above with updated list of bulb wattages, exposure time, developer mixture, developer temperature, etc...., I know that if I follow that recipe, I will have pretty consistent developed results as proven by myself to myself, however their are still flaws which will provide inconsistent etchings. I am still trying to eliviate these problems.
Do I think there are flaws with the film? No I don't. I just have not acheived the perfect combination for my system. There are many guys that will say that it is easy to make a circuit board. But they have already figured out there system. Photography exposure and developing is a science all on its own. It is not easy to achieve a perfect photograph or PCB until you have mastered the process of exposure and development. And between those two, the exposure process is the most difficult. The film must be exposed to a proper amount of light for a proper amount of time. This is paramount. If you have an improper exposure, you might as well throw it in the garbage or buy spray on photo-resist
If you are maintianing your developer temperature, I would imagine there are still problems with your exposure process.
Bruce
EDIT: Additionally, just when you think you have the developer at the proper temperature, let it set a minute, then recheck it again to ensure that it has remained the same or gone down in temperature, instead of rising.
In addition to my previous post, I will give you a tip that has helped me get more consistent results. There are a lot of videos out there that show guys rinsing there boards with cold running tap water just after developing the board. This turned out to be a waste of time and effort for me. Grab an empty five gallon bucket and fill it with cold water. Keep this bucket of cold water in close proximity of your developing tray. When developing your boards, leave them in the developer until you think they are very close to being fully developed, then pull them out of the developer and breifly dunk them into the bucket to rinse off the developer. Pull the board back out of the water and closely inspect the board for unwanted photo-resist. If you find unwanted photo-resist, put it back into the developer for a few seconds, then rinse and inspect it again. Continue this process until all unwanted photo-resist has been removed and then rinse the board within the bucket for one continuous minute.
Good tip about having the bucket of rinse water handy. :thumb:
One thing from my experience with DataK boards,
The film coating does go bad with age, I have used some ancient boards, that I purchased from an ancient electronics store.
I had to give up exposing them for one minute under a 100 watt IR bulb, instead out of frustration,
I put the board and artwork under the light of my portable sun.(800 watt grow lamp) for 5 minutes.
And have had great results in salvaging those old boards.
Brand new boards take about 30 seconds to a minute for exposure under the big light..
Comments
I have always wanted to attempt to expose screens and screenprint the board traces. Have you ever tried that method and were you successful?
Bruce
Yes I meant silk screen printing.
'
Have you tried any spray-on developer?
'
Have you found a place to get this in the USA? [EMAIL="'@Bruce"]'@Bruce[/EMAIL]
'
I have a few(more like several/OK a dozen)~1"sq. pcbs that I have botched the developer-film in my testing.The boards are fine,Just no developer film on them.
'
It would be nice to recycle these pcbs.(apply new photo film)
'
I'm also re-thinking the toner transfer method.So all hope is not lost with the botched pcbs.
I transfered a plan paper toner transfer to a copper pcb with really good results.(special heater set-up)
'
I'm just looking for something convenient that I can make at home for a one of pcb.
I was just discussing the same subject earlier today
And in answer to your question, no, I have not found anyone that sells Positiv 20 in the USA.
Walt, I am getting very close to producing very nice boards with my exposure box. By the end of today, I should have it whooped. I would suggest building one of these exposure box/cylinders, and then I will send you a complimentary exposure plate and exposure plate holder (with the exception of a few parts that could be purchased locally).
Bruce
We had some spray-on resist available some years ago that worked quite well, and I made a few boards using it. However, the formulation was changed (something to do with health and safety, I think) and the new stuff didn't work. I complained to someone from the company at a trade show, and he admitted that there was a problem.
A few members of the Homebrew PCB group buy dry-film resist and coat their own boards. It's only available from suppliers in large rolls, but some people resell smaller amounts to other hobbyists. Paradoxically, the best way to apply it at home with simple equipment is under water.
In an attempt to gain a little more control and not push the exposure box to it's limit, I exchanged the previously installed 40 watt bulbs for 25 watt bulbs. After (4) tests, with exposure times ranging from 1 minute to 5 minutes, I have come to the conclusion that the 25 watt bulbs are incompatable with the exposure box system. I would assume that the 25 watt bulbs are having a very difficult time of properly exposing the board while using vellum as a positive medium. I have decided to return to the use of 40 watt bulbs. Considering previous tests with the 40 watt bulbs, I will have to pay very close attention to the time clock, because exposures will now be under a minute. I now need a new clock that displays seconds. I am half-tempted to reappropriate the timer from my larger exposure box.
Bruce
I'm glad to see that I'm not the only one that can't find the spray on developer.
'
'
Test point
'
I think knowing what the film is made of would help to determine how to expose it.
I think I know the smell of the film after removing the protective cover layer.I think its vinyl acetate.This is used to make Latex.
Latex is very biodegradable by light sources.(UV,IR.temp.,etc.)
'
Just some added info to add/consider in the test realm.(I like details)
'
@Bruce
I'm glad to see your dialing in on the process.I still see some variables that are temperature related issues that need to be addressed.
I could be wrong.But if the film is Latex based then temperature will play a huge roll in the process.
I plan on looking at the exposer board temps in my next test run.And the room temps as well.
'
I'll report back with the Data I gather from these tests.
Here is an excerpt from another thead (http://forums.parallax.com/showthread.php?137511-Looking-For-Ideas-Temperature-Control) that specifies another problem with this particular PCB and developer. You may want to read this thread because it had some very good responses and feedback.
At this point, let me remind you that Philmore DATAK recommends a developer temperature between 100 and 110 degrees fahrenheit for their Premier boards, which is the type of board that I am currently testing.
Eventually I will create a final and more elegant solution to this problem in association with the coffee maker, but for now, I want to do some more testing with exposures, so this is my proposed temporary solution and procedure. On second thought, let me first tell you that I am using an oven-safe bowl in combination with the coffee maker to heat the developer. Anyhow, as you can imagine, it takes a little time to heat the coffee maker, the bowl, and the developer. Using a standard thermometer, like the one used to take a persons temperature, turn the coffee maker on and drive the temperature up. The thermometer that I have has a maximum temperature of 106 degrees fahrenheit. There is no way that I will be able to stop this drive in temperature right at the thermometer maximum, so I will simply exceed the maximum. I will then keep taking temperatures of the developer until the temperature reading registers approximately 105.9 degrees fahrenheit. At this point I will take my previously exposed PCB and set it in the developer. Considering that it takes a while to heat the solution up, it will also take a while to cool down, which should permit me with ample time to develop the board. It is not an elegant solution, but it should work until I get a permanent solution.
Bruce
I am definitely back in the ballpark.
I performed a similar procedure as stated in my previous post, except that I drove the temperature up to 102 degrees fahrenheit and then shut the coffee maker off because I knew the temperature would continue to rise. I then got a little impatient, because the thermometer remained off-scale, and I figured that it must be around 110 degrees fahrenheit. Needless to say that I ruined another sample board. I am not a person easily swayed by my own stupidity, so I immediately exposed another board and tested the developer temperature. The temperature reading was now at 104 degrees fahrenheit. Instead of heating another batch of developer, I plopped the newly exposed board into the previously used developer. Within approximately a minute to a minute and a half, I removed the best looking board that I have acquired from these experiments. I can't say that it is 100% perfect, but I would definitely give it a 95%. It's looking good.
I was not going to post this information until the experiments were complete, but just in case someone is reading this and following along, here is the current mixture of my developer used for Premier Pre-Sensitized Positive Acting Printed Circuit Boards from Philmore DATAK:
- 12 fluid ounces of tap water
- 3 grams of Rooto Crystals of Household 100% Lye Drain Opener (available at ace hardware)(caustic soda/sodium hydroxide)
Additionally, the current exposure was made with my exposure box/cylinder described at http://www.novelsolutionsonline.com/exposurebox.htm. It is a double-sided exposure and the board was exposed for a period of one minute with a 40 watt bulb on each side of the board.I am starting to get excited again
Bruce
EDIT: It is worth mentioning, that if you are using these boards and attempting an exposure with a different exposure setup, you may need to alter your bulb wattage, exposure time, etc... The exposure box/cylinder that I was using is constructed from tin and the bulbs are contained within a highly reflective housing.
I can now unequivocally state that the temperature of the developer is one of the primary factors in developing a nice board using the materials as stated in previous posts. I can clearly see an improvement and the difference after the developing process is complete. Developing times are now pretty consistent, and the photo-resist looks more intact than previous experiments.
I just did another exposure, but this time I increased the exposure time to 1 1/2 minutes with the hope that the photo-resist would dissolve more easily and leave less haze. I am happy to say that this exposure looks a little better than the last one. I am certain that the exposure time is not perfect just yet. So now I wonder whether to increase the exposure time just a little more or should I decrease it? I think I will bump it up another 15 seconds just to see the results. Since I am at this stage of the game, I could probably use the test procedure that Leon mentioned earlier in this thread, but I think I will continue with the way that I have been doing it so far, because at this point, I think I have a pretty good routine going and I believe it will only be just a few more exposures until I get it to the 100% mark.
To be perfectly honest, I would be happy walking into a print shop and having them make a positive for me, but the print shops in my area don't carry the proper equipment anymore.
Additionally, I would use transparencies, but I currently get a lot of streaking, therefore I am using vellum to get a better quality positive.
I can be a very picky person, and it definitely holds true in this instance. I am sure a lot of people would have been more than pleased with some of my results so far, but like I said, I am striving for perfection.
Just wait until I post some pictures before giving vellum a bad reputation.
At this point, everything looks good except the 0.004" trace, which still looks a little fuzzy.
I do not have any pictures just yet. My brother is the one with all the nice camera equipment. When I get the process perfect, I will run a sample to his house and use his nice Canon with telephoto zoom. The sample board is about the size of a quarter and it has a few areas of pretty fine detail. So when I take the pics, I will take them next to a quarter for size comparison.
However, here is the design that I am using for front and back.
Exposure Unit: My PCB Exposure Box/Cylinder listed at the beginning of this thread.
PCB Material: Philmore DATAK Premier Series (1/16" 2oz. double sided FR-4 board with positive acting photo-resist film)
Test Size: 0.937" X 0.937"
Front Test Pattern: Gradient lines 0.004" - 0.008" in 0.002 increments.
Rear Test Pattern: Gradient lines 0.010" - 0.075" in 0.005 increments.
Top And Bottom Copper Masks: Please refer to the updated images attached below.
Positive Medium: Premium Matte Laser Film (0.004") Top Coated With Acrylic Krylon Crystal Clear Satin (#51313)
Exposure Lamps: (2) New 60W/120V Sylvania A15 Ceiling Fan Light Bulbs (60A15/CL/2PK/BL)
Exposure Time: 2 minutes and 5 seconds
Developer Mixture:
- 4 grams of Rooto Crystals of Household 100% Lye Drain Opener (available at ace hardware)(caustic soda/sodium hydroxide) to 1 pint of tap water
Developer Temperature: 106 degrees fahrenheit'
Looking forward to the PICs of the sample PCB's
'
It sounds like you have " NAILED-IT "...!!!
'
I'd like to recommend a test with a real circuit and a copper poor before (you) call this a perfect set-up.I have found that things really change with a copper poor.
'
Of coarse this might be a little to early in the design state!
'
I'm just excited about being able to make a nice "one of PCB" at home!
'
My test results are running right close to yours,So I think we (Your) very close to perfection.
'
I'll be the first to buy your exposure set-up when its ready.
For my next sample, I am going to duplicate my business card in copper and tin coat it
I won't get excited until I get the next PCB driller constructed and programmed, but everything is looking quite promising. The PCB cutter works like a dream and I just love that machine
I do not sell the entire expose box assemblies due to laws concerning underwriting. I only sell the hardware kits and exposure plate assemblies for the exposure box. In a previous post, I suggested that you make one of these, and said that I would give you a complimentary exposure plate assembly with the exception of a few minor parts. I still suggest the same. It is a very nice little unit for doing boards 3 X 4 or less.
Bruce
'
PM sent
With the boards now being processed with the developer being in the temperature range as specified by the board manufacturer, the results are now much more consistent, however I am still toying with the process just a little. All of the traces widths are turning out nice, including the 0.004", but the fine print of the web address on the sample has been giving me some problems with clarity. I am still working on that problem and I may have to resort to transparancies as Leon stated, but I am still attempting to accomplish a crystal clear photograghic image with vellum.
Additionally, after making my awesome PCB cutter, I got so excited to start making samples that I got a little sloppy when making my exposure plate and provided just a little too much clearance for the board to move around. With this additional, unnecessary clearance, if the positive image of vellum is not perfectly aligned with the board, it produces small unwanted wire traces along the unaligned edges of the board. So it is needless to say that I need to make a more accurate exposure plate for myself, just as if I was creating one for a customer. I want this sample to sparkle with quality.
And as a side note, just in case nobody caught the edit in the "un-perfect process" above, I have bumped up the exposure time from 1 minute and 45 seconds to 2 minutes.
Bruce
I have made a new exposure plate for making the samples and this exposure plate has much tighter tolerances than the previous one. With these tighter tolerances, I should be able to produce much better looking samples. I will return to the experimentation process sometime Sunday evening.
Please stay tuned.
Bruce
I have recently learned that I was apparently no where near the perfect process yet and I am still learning the intricacies pertaining to the use of my exposure box in combination with the Philmore DATAK Premier Series Presensitized Positive Acting PCBs. Considering what I have learned during this experimentation process, I cannot over-emphasize the importance of the developer temperature and I have established the fact that all of my experiments prior to having the developer at a proper temperature were utterly useless.
After doing some more research and considering that I am now developing at a controlled temperature, I decided to bump the bulb wattages back upto 60 watts and try these bulbs again at an exposure time of 2 minutes. With the bulbs at 60 watts, exposing the boards for 2 minutes, and having the developer at a temperature of 104 fahrenheit, I have now produced the best looking developed board so far. I am now further convinced that I am still nowhere near the perfect process yet and that it is still a learning process.
To obtain even more control, with the intent to eliminate potential error or deviation from the process, I have decided to set aside a specific area for PCB processing. This area will not have any access to sunlight or stray rays from fluorescent lighting, and a safelight will be provided by a yellow 25 watt bug light as suggested by the board manufacturer.
Bruce
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I have run some more tests with a highly controlled environment.Much like the one you have mentioned above.
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I'm still seeing an unexplained variable.(Inconsistencies from one board to another)
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I think this variable is the age of the film on the DataK board.
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Have you noticed anything like this?
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Not sure how to read the date code on the DataK boards...If there is a date code.
You have to imagine that my controlled environment is constantly changing
Additionally, removing the inconsistencies is the main reason behind testing
The largest inconsistencies that I have noticed has been due to developer temperature and mixture. Now that I am controlling the temperature, I am having much better consistency. However, I am getting ready to change the mixture of the developer again, because I believe I have the "exposure" process pretty well nailed (which may still need a little altering here and there).
I do not know how you are performing your tests, but my main goal right now is trying to achieve the best exposure. I would imagine that I have developed at least 40 - 60 exposure tests, but I have only etched about four samples. You must keep in mind that you will never get a good etching unless your exposure and photoresist are in good shape. Before etching any boards, try to achieve a board that has a crystal clear image of photo-resist without any remaining haze on the board. Above all else, keep in mind that it is a photographic process and that you are looking for the best image possible with the photo-resist, and that the etching is a direct by-product of this image.
If you refer to my post above with updated list of bulb wattages, exposure time, developer mixture, developer temperature, etc...., I know that if I follow that recipe, I will have pretty consistent developed results as proven by myself to myself, however their are still flaws which will provide inconsistent etchings. I am still trying to eliviate these problems.
Do I think there are flaws with the film? No I don't. I just have not acheived the perfect combination for my system. There are many guys that will say that it is easy to make a circuit board. But they have already figured out there system. Photography exposure and developing is a science all on its own. It is not easy to achieve a perfect photograph or PCB until you have mastered the process of exposure and development. And between those two, the exposure process is the most difficult. The film must be exposed to a proper amount of light for a proper amount of time. This is paramount. If you have an improper exposure, you might as well throw it in the garbage or buy spray on photo-resist
If you are maintianing your developer temperature, I would imagine there are still problems with your exposure process.
Bruce
EDIT: Additionally, just when you think you have the developer at the proper temperature, let it set a minute, then recheck it again to ensure that it has remained the same or gone down in temperature, instead of rising.
In addition to my previous post, I will give you a tip that has helped me get more consistent results. There are a lot of videos out there that show guys rinsing there boards with cold running tap water just after developing the board. This turned out to be a waste of time and effort for me. Grab an empty five gallon bucket and fill it with cold water. Keep this bucket of cold water in close proximity of your developing tray. When developing your boards, leave them in the developer until you think they are very close to being fully developed, then pull them out of the developer and breifly dunk them into the bucket to rinse off the developer. Pull the board back out of the water and closely inspect the board for unwanted photo-resist. If you find unwanted photo-resist, put it back into the developer for a few seconds, then rinse and inspect it again. Continue this process until all unwanted photo-resist has been removed and then rinse the board within the bucket for one continuous minute.
I hope this will help you get better results.
Bruce
One thing from my experience with DataK boards,
The film coating does go bad with age, I have used some ancient boards, that I purchased from an ancient electronics store.
I had to give up exposing them for one minute under a 100 watt IR bulb, instead out of frustration,
I put the board and artwork under the light of my portable sun.(800 watt grow lamp) for 5 minutes.
And have had great results in salvaging those old boards.
Brand new boards take about 30 seconds to a minute for exposure under the big light..
-Tommy
I had my first problem with the film early this morning. Two dots were on the board after developing with no explanation for their existence.