Construction Of A PCB Prototyping Table
idbruce
Posts: 6,197
Hello Everyone
As mentioned in another thread, I intend to make myself a PCB Prototyping Table, which should make the whole process a lot less troublesome and therefore a whole lot more enjoyable. In the past, my process consisted of an unorganized attempt to successfully make PCBs. Since the creation of my exposure box/cylinder, I have learned a lot pertaining to the creation of PCBs, mostly through the process of trial and error. In my last experiment pertaining to PCBs, I learned how to successfully achieve the proper temperature for the developer, which is of the utmost importance for the system and setup that I use. As a result of that experiment, I came up with the idea to create myself a PCB Prototyping Table. This initial post will discuss some of the materials being used, a rough draft for my first attempt, and some basic ideas. In the future, there will eventually be support electronics to control the length of the exposures, as well as heating control for the developer and etchant, but that will have to wait for now.
In the following discussion(s), I will tell you what I intend to do, much of which is currently dictated by the materials that I have available. Of course, if you decide to build a PCB Prototyping Table for yourself, you may have different ideas than me and different materials available.
For my table base, I will be using a Cosco table that I bought at KMart or Walmart several years back. It is nothing fancy, just a metal frame, with folding legs and a very flimsy, vinyl coated, 3/16" masonite top. In the future, I will eventually laminate some formica onto a sheet of 1/2" or 3/4" plywood for stability and easy clean up, and swap out the tops, but for now, I just want to experiment to find a good working solution. And just so you can visualize what kind of table I am starting with, the link below is a very close representation. The link shows a couple five piece sets, but only the table is required, and I am sure you can find the table seperately. It is also noteworthy to mention, that all the recess items will have to be removed before the table legs can be folded for transportation, and most likely the vinyl top will rip and tear during the construction process.
Some of the other parts that I will be using include:
In the attachment provided below, you will find the general layout that I will be using. The areas marked by the red Xs represent corner baces installed by the manufacturer, and therefore, those areas cannot be used for recessing. In the area marked "Recessed Exposure Box/Cylinder", only the bottom half will be recessed. During setup time for the exposure process and after the exposure process, the top half will be removed and placed in the area marked "Temporary Holding Area". And if I am not mistaken, the rest of the diagram should be self-explanatory. As for the (2) 125 watt heat lamps, these will be placed under the developer and etchant trays to heat these solutions upto the proper temperature. I have also attached a photo of my Exposure Box/Cylinder for better visualization. When I am done with the initial prototype of the table, I will upload a few photos for your viewing pleasure.
Additionally, if you are seriously interested in making PCBs, here is a list of my other threads pertaining to DIY PCBs:
Bruce
As mentioned in another thread, I intend to make myself a PCB Prototyping Table, which should make the whole process a lot less troublesome and therefore a whole lot more enjoyable. In the past, my process consisted of an unorganized attempt to successfully make PCBs. Since the creation of my exposure box/cylinder, I have learned a lot pertaining to the creation of PCBs, mostly through the process of trial and error. In my last experiment pertaining to PCBs, I learned how to successfully achieve the proper temperature for the developer, which is of the utmost importance for the system and setup that I use. As a result of that experiment, I came up with the idea to create myself a PCB Prototyping Table. This initial post will discuss some of the materials being used, a rough draft for my first attempt, and some basic ideas. In the future, there will eventually be support electronics to control the length of the exposures, as well as heating control for the developer and etchant, but that will have to wait for now.
In the following discussion(s), I will tell you what I intend to do, much of which is currently dictated by the materials that I have available. Of course, if you decide to build a PCB Prototyping Table for yourself, you may have different ideas than me and different materials available.
For my table base, I will be using a Cosco table that I bought at KMart or Walmart several years back. It is nothing fancy, just a metal frame, with folding legs and a very flimsy, vinyl coated, 3/16" masonite top. In the future, I will eventually laminate some formica onto a sheet of 1/2" or 3/4" plywood for stability and easy clean up, and swap out the tops, but for now, I just want to experiment to find a good working solution. And just so you can visualize what kind of table I am starting with, the link below is a very close representation. The link shows a couple five piece sets, but only the table is required, and I am sure you can find the table seperately. It is also noteworthy to mention, that all the recess items will have to be removed before the table legs can be folded for transportation, and most likely the vinyl top will rip and tear during the construction process.
Some of the other parts that I will be using include:
(2) - 1-1/2 X 6 X 6 Rubbermaid storage containers for the developer and etchant solutions
(3) - Empty 12 lb. buckets of DAP Wallboard Joint Compound, for rinse buckets and glove holder
(2) - 125 watt Westinghouse heat lamps
As well as various other electrical and construction components (I may list these items later as I build)
(3) - Empty 12 lb. buckets of DAP Wallboard Joint Compound, for rinse buckets and glove holder
(2) - 125 watt Westinghouse heat lamps
As well as various other electrical and construction components (I may list these items later as I build)
In the attachment provided below, you will find the general layout that I will be using. The areas marked by the red Xs represent corner baces installed by the manufacturer, and therefore, those areas cannot be used for recessing. In the area marked "Recessed Exposure Box/Cylinder", only the bottom half will be recessed. During setup time for the exposure process and after the exposure process, the top half will be removed and placed in the area marked "Temporary Holding Area". And if I am not mistaken, the rest of the diagram should be self-explanatory. As for the (2) 125 watt heat lamps, these will be placed under the developer and etchant trays to heat these solutions upto the proper temperature. I have also attached a photo of my Exposure Box/Cylinder for better visualization. When I am done with the initial prototype of the table, I will upload a few photos for your viewing pleasure.
Additionally, if you are seriously interested in making PCBs, here is a list of my other threads pertaining to DIY PCBs:
ATTN: PCBers SUBJECT: New website and exposure box design for your creative needs
DVD Laser Diode And Optical Block (Future Laser Photoplotter)
DIY PCB Fabrication For The Sake Of Science And Education
Looking For Ideas - Temperature Control
What is the very best way to get a positive image for PCB making these days?
New Project/New Experiment - PCB Etchant And Developer Heaters
http://forums.parallax.com/showthread.php?139257-New-Project-New-Experiment-PCB-Etchant-And-Developer-Heaters
http://forums.parallax.com/showthread.php?139257-New-Project-New-Experiment-PCB-Etchant-And-Developer-Heaters
Bruce
616 x 608 - 60K
513 x 507 - 18K
Comments
Wish me luck.
Bruce
As for the cutouts, the trays and the buckets fit very nicely, however the cutout for the lower half of the exposure box/cylinder is just a bit to tight. One time around the perimeter with a half round file, and the exposure should fit fairly snug.
I only have three main things left to do, before I can start using my new PCB Prototyping Table.
- I must make the lower half of the exposure box/cylinder capable of being mounted in the proper cutout.
- I must build a platform and wire up a couple of lamp sockets for the heat lamps that will warm up the developer and etchant trays.
- I must build some type of shroud to go around the heat lamps to prevent light from escaping.
This part of the project turned out to be a lot easier than I anticipated, and I am very glad that it is over with. It won't be long until I have the perfect setup for exposing, developing, and etching my own circuit boards.Bruce
Firstly, in the previous post, and in another thread, there has been discussion of the prevention of escaping light from the heat lamps. As mentioned in the previous thread, it was my intention to build a shroud around the heat lamps to prevent this light from escaping, but this morning, I put some more thought into maintaining the temperature of the solutions as compared to simply heating them up to the required temperature and then shutting the lamps off. Considering that the Rubbermaid bowls that I am using as my trays are translucent, this would become a major problem during the development process if the solution needed to be reheated. So in addition to preventing stray light from escaping laterally, I must now also consider the fact that I really don't want any light reaching the trays, because of their translucency. The heat lamps are perfect for heating the developer and etchant solutions, because when the lamps are turned off, the temperature of the solutions stop climbing almost instantly, and whatever light blocking solution I come up with, I want to maintain this benefit. While drinking my early morning coffee, I was thinking of several possible solutions, and then I remembered seeing a light bulb encased in aluminum foil for some type of photography purpose. At the moment, I am assuming that this will be a perfect light blocking solution for me. The aluminum foil should heat up and dissipate heat very quickly while blocking the light rays. However, wrapping the light bulbs in aluminum foil has some disadvantages and hazards associated with it. By wrapping the heat lamp in aluminum foil, the lamp will become very hot and very quickly, which I am sure will shorten the life of the bulb, perhaps almost immediately. And furthermore, it might get hot enough to melt the aluminum foil or burn a hole through it. Another issue is that aluminum makes a nice electrical conductor and must be used with care around the lamp sockets. Needless to say that I will be experimenting with this idea later today, which would eliminate the need to build a light shroud as mentioned in the previous post.
Secondly, as mentioned in the previous post, I mentioned that I was going to smear silicone around the inside perimeter of each cutout to help hold the vinyl covering in place. Without going into great detail about my decision, I have decided to use DAP 230 (Clear) Advanced Kitchen & Bath Latex Sealant instead of a silicone adhesive.
Okay it is now time to go back to my project and bring it closer to finalization.
Bruce
The vinyl is now very secure to the table top as a result of the application of the DAP 230 (Clear) Advanced Kitchen & Bath Latex Sealant around the inside perimeters of the cutouts. Even though I was considering making another top for the table in the future, this one is now appearing to be very suitable for the intended purpose.
For the last couple of hours, I have been gathering materials to make my platform for the heat lamps. I don't remember if I mentioned it before, but I have also decided to build another platform on top of this platform for the exposure box/cylinder to rest upon, instead of mounting it to the table, which will result in a more portable solution. Anyhow, as mentioned in one of my other threads, a friend of mine had given me several sheet metal structures quite a while ago, and since then, they have been great dust collectors. Two of the structures are identical 5-sided rectangles with mounting flanges going around the perimeter. Just for giggles, I pulled them out and compared the length of these structures to the width of the table, and guess what, they were practically the same measurement. So I have decided to put one structure on top of the other and bolt them together to make a complete 6-sided enclosure, which would be something similar to a good size electrical junction box. In addition to the surplus sheet metal structures, I also have quite a few square/round tee-legs laying around from previous projects. It is now my intent to mount one of these legs on each end of the bottom sheet metal structure, to raise the final platform upto the desired height for heating the developer and etchant trays. The top sheet metal structure will be modified to easily adapt two pull string porcelain lamp holders and a duplex receptacle, as well as another pull string switch. So basically the top sheet metal platform will contain all of the electrical devices and wiring to control the exposure box and heat lamps. As mentioned earlier, I am not going to build a controller for this setup at this time, so everything will have to be controlled manually until I get to that point. To assist in manual operation of the equipment and to make my life much easier, all equipment will be controlled by pull strings extending upward from the heat lamp platform to the table top. As mentioned, there will be a pull string porcelain lamp holder for each heat lamp. As for the exposure box/cylinder, which also contains two lamps, these lamps are cord and plug connected and will end up plugging into the duplex receptacle. However, the duplex receptacle will be powered by a pull string switch. In the end, there will be three pull strings extending to the table top, one to control both lamps in the exposure box/cylinder, one to control the heat lamp for the developer, and one to control the heat lamp for the etchant.
Sounds like a good plan to me
Bruce
I was feeling a little lazy today, so the progress is going a little slow, however, the heat lamp platform is well under way. I cut two legs to the required height, drilled and threaded some mounting holes, drilled matching mounting holes in the lower sheet metal platform, and mounted the legs. Just to check everything out, I placed the bottom section of the heat lamp platform under the table, I placed the top section of the heat lamp platform upon the bottom section, and I then placed the lamp and socket assemblies on top to check the fit and distance from the trays. It was a perfect fit, with the top of the heat lamps being approximately 2-1/2" from the bottom of the trays, which is exactly what I wanted. However, as determined by the trial fit, I can clearly see that I will have to be very creative with the pull string routings, because the buckets are right in the way of where I want to route them, which was a huge oversight on my part.
Additionally, through the trial fit, it was determined that I will need to place at least a 3-1/2" platform on top of the heat lamp platform for the exposure box/ cylinder to rest upon.
Bruce
As mentioned in the previous post, there was a huge design oversight on my part pertaining to the routing of the pull strings. The recessed buckets became obstacles for the intended path of the pullstrings. After a little experimentation, I discovered that the pullstrings switches were quite capable of being switched on and off from a lateral or slightly downward angle position. Considering that the heat lamp platform is 12" wide, I am going to mount three eyescrews near the widths edge, spaced apart according to the pullchains point of origin. So the pullchains will extend basically lateral for a distance of approximately 5" and then angle upward toward the table top to another set of eyescrews. This routing provides ample clearance in regards to the recessed buckets and should provide smooth operation.
It is now time to start laying out the top section of the heat lamp platform, drill and thread some holes, and mount my components.
Bruce
As mentioned in an earlier post, I was going to utilize a single duplex receptacle for plugging in both halves of the exposure box/cylinder. Upon further thought and consideration that there will be a substantial amount of liquid on the table, I have also decided to install a Ground Fault Circuit Interrupter receptacle, in addition to the standard duplex receptacle. Additionally, most likely this table will be placed upon concrete, and who knows if a GFCI receptacle will be in close proximity. And it is always nice to have an extra GFCI receptacle available to plug into for the sake of personal protection from electrocution.
I will provide household current and voltage to the LINE side of the GFCI receptacle, and from the LOAD side of the GFCI receptacle I will provide power to both of the pull string porcelain lamp holders and the pull string switch which will provide power to the duplex receptacle that powers the exposure box/cylinder.
Always remember, SAFETY FIRST
Bruce
But of course that will have to come right after a short little nap
I am now at the point where all electrical devices have been wired up and tested. As mentioned in Post #6, I need another platform 3-1/2' tall for the exposure box/cylinder to rest upon, and that is what I am currently working on. This platform will consist of (3) 5/8" diameter aluminum posts 3-1/2" long and a tin can lid, which is a surplus lid left over from building the exposure box/cylinder. Each post will be drilled on both ends and tapped with 10-32 threads. The tin can lid will be bolted to the (3) posts upside-down and the other end of the posts will be bolted to the heat lamp platform. After bolting this platform to the heat lamp platform, I can then bolt the top section of the heat lamp platform to the bottom section of the heat lamp platform with (10) 10-32 X 1/2" screws, at which point it will basically be complete and ready for testing on actual boards.
As a final comestic touch mixed with American pride, I will eventually paint the buckets red, white, and blue, and letter the buckets respectively U.S.A. Additionally, I will have to find a nice "Made In The U.S.A." decal for the front of the heat lamp platform.
It is noteworthy to mention that in addition to providing extra safety and a convenient electrical outlet, the previously mentioned GFCI receptacle also provides a convenient means for shutting off power to the entire unit and for testing. The GFCI receptacle provides a "Test" button for testing the receptacle to ensure that it is working properly. When the "Test" button is pressed, it shuts off available power to the receptacle and any electrical circuitry attached to the "LOAD" side of the GFCI receptacle. After each and every use, before leaving the work area, I will press the "Test" button to disconnect all possible power.
Photos coming soon.
Bruce
With the exception of a few cosmetic touches, the PCB Prototyping Table is finally complete and ready for some serious PCB prototyping. I am very happy with it, and it is one slick setup. Of course you will just have to take my word for it until I have some photos taken. Most likely I will be taking it for a test run later this evening.
Bruce
Since I have a few minutes available, I would like to tell you about another nice feature of this PCB Prototyping Table. After the construction of the PCB Prototyping Table, it became necessary to move it and get it completely out of the way. So I simply removed the lower half of the Exposure Box/Cylinder, the three buckets, and the two trays, from the table surface. I then disconnected the pull chains in close proximity of the pull chain lights and the pull chain switch. I then removed the three pull chains from the PCB Prototyping Table and dropped them into glove bucket. After sealing off the three buckets and the two trays with the appropriate lids, I folded up the table and placed it against the wall. I then positioned the heat lamp platform in front of the table on the floor. The three buckets and two trays easily fit under the heat lamp platform.
RESULT:
- Neat and compact storage
- Tear down time 4 minutes.
Yeah babyBruce
I wanted to get a little practice using my new table, so I exposed, developed, and etched one of my small samples on the table this evening. All things considered, it went very smoothly and I am very happy with it. However, now that I am using double-layer transparencies and have a better grip on the temperature of the developer, I can clearly see that I will need a longer exposure time and a slightly stronger mix of developer. But for the most part, the sample came out looking good. It won't be long now, and you guys should start seeing some pretty nice boards from me.
Bruce
Over the last couple days, I have been experimenting with my new PCB Prototyping Table and striving to perfect my production process. During this time, I have really come to appreciate the PCB Prototyping Table, because it is quick and easy to produce PCBs, however there is one drawback worth mentioning. At first it seemed like the perfect setup, but as it turns out, I just wish I had a little more room on the right-hand side for miscellaneous stuff, such as, ashtray, vernier calipers, file, magnifying glass, rags, thermometer, timer, storage area for photo masks, etc...
If you intend to make a PCB Prototyping Table, please consider the use of a little longer table or custom make another top. When I find a little more time, I will probably make another table or table top with a little more storage area on the right-hand side.
Bruce
I am still perfecting my process, however I am getting very close. Taking unnecessary photos is a real pain for me, because I do not have the proper photo equipment. When I think I have something worthy of OOHHSS and AAWWSS, believe me I will take photos.
I have a sample in front of me, where the back-side is almost immaculate, but the front-side was not properly developed (residual photo resist haze) due to inadequate safe lighting. The back-side is definitely worthy of a photo, but I will wait until the whole sample is 100% perfect.
The attachment below represents the backside of the sample that is in front of me.
You should know me well enough by now that I don't tell tall tales.
Bruce
I have not even tested registration yet, because I know it will be very close to dead center.
To understand my degree of certainty, you have to understand the premise upon which my Exposure Box/Cylinder is built. There is very little room for misalignment. The bottom mask, top mask, and PCB material are all surrounded by a perimeter, and their width and length dimensions are all within a couple thousandths of each other, and just a couple thousandths smaller than the perimeter. The tight tolerances in conjunction with the perimeter pretty much guarantee acceptable registration alignment.
Bruce
Your questions just lead me to a brilliant idea
Bruce